Fix purge filter in DELETE/agents

[Lifka]

Hi team,

this PR fixes purge filter in DELETE/agents (issue #121).

Sample

$ cat /var/ossec/etc/client.keys
001 agent001 any aad3f2f3dc3ec3b2ffc76ecd0e74fbb8657bb09253abd0c9c06b1908328ae370
002 agent002 any aad3f2f3dc3ec3b2ffc76ecd0e74fbb8657bb09253abd0c9c06b1908328ae370
003 agent003 any aad3f2f3dc3ec3b2ffc76ecd0e74fbb8657bb09253abd0c9c06b1908328ae370
004 agent004 any aad3f2f3dc3ec3b2ffc76ecd0e74fbb8657bb09253abd0c9c06b1908328ae370
005 agent005 any aad3f2f3dc3ec3b2ffc76ecd0e74fbb8657bb09253abd0c9c06b1908328ae370
006 agent006 any aad3f2f3dc3ec3b2ffc76ecd0e74fbb8657bb09253abd0c9c06b1908328ae370
007 agent007 any aad3f2f3dc3ec3b2ffc76ecd0e74fbb8657bb09253abd0c9c06b1908328ae370
008 agent008 any aad3f2f3dc3ec3b2ffc76ecd0e74fbb8657bb09253abd0c9c06b1908328ae370
009 agent009 any aad3f2f3dc3ec3b2ffc76ecd0e74fbb8657bb09253abd0c9c06b1908328ae370
010 agent010 any aad3f2f3dc3ec3b2ffc76ecd0e74fbb8657bb09253abd0c9c06b1908328ae370

$ curl -u foo:bar -k -X DELETE "http://127.0.0.1:55000/agents?pretty&status=neverconnected&older_than=1s&purge=true"
{
   "error": 0,
   "data": {
      "msg": "All selected agents were removed",
      "older_than": "1s",
      "affected_agents": [
         "001",
         "002",
         "003",
         "004",
         "005",
         "006",
         "007",
         "008",
         "009",
         "010"
      ],
      "total_affected_agents": 10
   }
}

$ cat /var/ossec/etc/client.keys

Regards,
Javi.

[mgmacias95]

Should the purge argument be removed from the body? If it is sent in a JSON, the request will fail. I think it could be much better to accept the argument in the body and in the query.

[mgmacias95]

If the purge argument is present in the query:

• It can be 'true'.
• It can be empty.

If it is present in the body:

• It can be true.
• It can be 'true'.

[jesuslinares]

Let's allow the purge in both places: query and body. The most restrictive wins.