Qualify request to time-of-day sync with connected check.

This qualifies the call to '__connman_timeserver_sync' with an
'is_connected' check on the new state of the service in
'__connman_service_ipconfig_indicate_state'. In fact, this leverages
the same conditional that 'nameserver_add_all' is also subject to.
This avoids a heap-use-after-free segmentation fault that can occur
when a network service goes away following link loss or a disable of
the corresponding technology.

Without this qualification, the network service going away will invoke
'__connman_timeserver_sync' with the
'CONNMAN_TIMESERVER_SYNC_REASON_STATE_UPDATE' reason as it cycles from
online/ready to disconnect. As currently implemented, the timeserver
code interprets this as a request to initiate time-of-day synchroninzation
with time services using the name and time services of that disappearing
service. As a result, this has two downstream impacts:

  1. In a multi-service connectivity environment, the junior service that
     was promoted when the senior service was disconnected and was set as
     the active service for time services when 'default_changed' was
     invoked is undesireably displaced by the disconnecting service.

  2. The implication of (1) is that the time service now holds a weak
     reference to the disappearing service in 'ts_service' rather than
     the promoted and new default service. Consequentl, when 'sync_next'
     is next called by time services, it will attempt to get the name
     or time servers for the disconnecting service. Unfortunately,
     these which have gone away, as 'service_free' was invoked on the
     disconnected service after it was wound down. It is the access to
     these name or time servers on the deallocated service object that
     causes the heap-use-after-free segmentation fault.

The address sanitizer report is as follows:

    =================================================================
    ==526==ERROR: AddressSanitizer: heap-use-after-free on address 0x72603898 at pc 0x0009b451 bp 0x7e9678f8 sp 0x7e9678fc
    READ of size 4 at 0x72603898 thread T0
        #0 0x9b44e in connman_service_get_nameservers:service.c:2896 (/usr/sbin/connmand+0x9b44e)
        #1 0xd485e in ts_set_nameservers:timeserver.c:387 (/usr/sbin/connmand+0xd485e)
        #2 0xd4930 in sync_next:timeserver.c:187 (/usr/sbin/connmand+0xd4930)
        #3 0xd4e6a in resolv_result:timeserver.c:141 (/usr/sbin/connmand+0xd4e6a)
        #4 0x37b5a in sort_and_return_results:gresolv.c:522 (/usr/sbin/connmand+0x37b5a)
        #5 0x385e4 in query_timeout:gresolv.c:547 (/usr/sbin/connmand+0x385e4)

    0x72603898 is located 88 bytes inside of 408-byte region [0x72603840,0x726039d8)
    freed by thread T0 here:
       #0 0x76a0d264  (/lib/libasan.so.8+0x8d264)

    previously allocated by thread T0 here:
        #0 0x76a0da6c in calloc (/lib/libasan.so.8+0x8da6c)
        #1 0x925b4 in connman_service_create (/usr/sbin/connmand+0x925b4)
        #2 0x9294c  (/usr/sbin/connmand+0x9294c)
        #3 0x9e844  (/usr/sbin/connmand+0x9e844)
        #4 0x7dda6  (/usr/sbin/connmand+0x7dda6)
        #5 0x7ea18 in connman_network_set_group (/usr/sbin/connmand+0x7ea18)
        #6 0x3da36  (/usr/sbin/connmand+0x3da36)
        #7 0x3db56  (/usr/sbin/connmand+0x3db56)
        #8 0xd057c  (/usr/sbin/connmand+0xd057c)
        #9 0xd0882  (/usr/sbin/connmand+0xd0882)
        #10 0xd28da  (/usr/sbin/connmand+0xd28da)
        #11 0xd2ca4  (/usr/sbin/connmand+0xd2ca4)

   SUMMARY: AddressSanitizer: heap-use-after-free (/usr/sbin/connmand+0x9b44e) in connman_service_get_nameservers

src/service.c

@@ -6538,11 +6538,12 @@ int __connman_service_ipconfig_indicate_state(struct connman_service *service,
 	else
 		service->state_ipv6 = new_state;
 
-	if (!is_connected(old_state) && is_connected(new_state))
+	if (!is_connected(old_state) && is_connected(new_state)) {
 		nameserver_add_all(service, type);
 
-	__connman_timeserver_sync(service,
-				CONNMAN_TIMESERVER_SYNC_REASON_STATE_UPDATE);
+		__connman_timeserver_sync(service,
+					CONNMAN_TIMESERVER_SYNC_REASON_STATE_UPDATE);
+    }
 
 	return service_indicate_state(service);
 }