Fix delete query error in elasticsearch

Change elasticsearch API to query delete in last versions.

Old format:
{ 
   "query_string" : { 
        "query" : "some_query"     
   } 
} 

New format(after version 1.2.0 or early):
{ 
   "query" : { //added 
    "query_string" : { 
         "query" : "some_query"     
    } 
    } 
}