Fix Cassandra service status definition

Reasons:
 - At slow environment (small flavors, etc.),
   for certain reasons Cassandra instances are in SHUTDOWN state
   for short period of time. This issue breaks assertion
   in int-test that waits for guest to reach ACTIVE state.

Changes:
 - adding validation for Cassandra log file:
   - if status check exec will exit with exit code equals to '1' instead of '0'
     Cassandra log file will be checked for modifications during specific
     time range (at least 5 seconds). If log wouldn't be modified,
     Trove guest will report its status as SHUTDOWN.

Change-Id: I6009e4c0979abb9a469aed4d3cf2b0f53df4c046
Closes-Bug: #1314980