enable safe reboot for multidut snappi cases. (sonic-net#14882)

Description of PR
Summary:
Current snappi multidut tests wait 15 minutes to finish a reboot as the default waiting time is 900 seconds for chassis.
However, when using safe reload, it will finish the reboot in 10 minutes. Also, existing non multidut test cases have changed to use safe reboot as well.
Therefore, setting multidut cases to use safe reboot.

Approach
What is the motivation for this PR?
reduce reboot time for multidut snappi cases.

How did you do it?
Use safe reboot.

How did you verify/test it?
Tested on lab devices.

co-authorized by: jianquanye@microsoft.com

tests/snappi_tests/multidut/pfc/test_multidut_pfc_pause_lossless_with_snappi.py

@@ -259,7 +259,7 @@ def test_pfc_pause_single_lossless_prio_reboot(snappi_api,                  # no
 
     for duthost in [snappi_ports[0]['duthost'], snappi_ports[1]['duthost']]:
         logger.info("Issuing a {} reboot on the dut {}".format(reboot_type, duthost.hostname))
-        reboot(duthost, localhost, reboot_type=reboot_type)
+        reboot(duthost, localhost, reboot_type=reboot_type, safe_reboot=True)
         logger.info("Wait until the system is stable")
         wait_until(180, 20, 0, duthost.critical_services_fully_started)
 
@@ -349,7 +349,7 @@ def test_pfc_pause_multi_lossless_prio_reboot(snappi_api,                  # noq
 
     for duthost in [snappi_ports[0]['duthost'], snappi_ports[1]['duthost']]:
         logger.info("Issuing a {} reboot on the dut {}".format(reboot_type, duthost.hostname))
-        reboot(duthost, localhost, reboot_type=reboot_type)
+        reboot(duthost, localhost, reboot_type=reboot_type, safe_reboot=True)
         logger.info("Wait until the system is stable")
         wait_until(180, 20, 0, duthost.critical_services_fully_started)
 

tests/snappi_tests/multidut/pfc/test_multidut_pfc_pause_lossy_with_snappi.py

@@ -250,7 +250,7 @@ def test_pfc_pause_single_lossy_prio_reboot(snappi_api,             # noqa: F811
 
     for duthost in [snappi_ports[0]['duthost'], snappi_ports[1]['duthost']]:
         logger.info("Issuing a {} reboot on the dut {}".format(reboot_type, duthost.hostname))
-        reboot(duthost, localhost, reboot_type=reboot_type)
+        reboot(duthost, localhost, reboot_type=reboot_type, safe_reboot=True)
         logger.info("Wait until the system is stable")
         wait_until(180, 20, 0, duthost.critical_services_fully_started)
 
@@ -340,7 +340,7 @@ def test_pfc_pause_multi_lossy_prio_reboot(snappi_api,          # noqa: F811
 
     for duthost in [snappi_ports[0]['duthost'], snappi_ports[1]['duthost']]:
         logger.info("Issuing a {} reboot on the dut {}".format(reboot_type, duthost.hostname))
-        reboot(duthost, localhost, reboot_type=reboot_type)
+        reboot(duthost, localhost, reboot_type=reboot_type, safe_reboot=True)
         logger.info("Wait until the system is stable")
         wait_until(180, 20, 0, duthost.critical_services_fully_started)