gluster: Refactored GlusterTaskSyncJob

Rafactored the class GlusterTaskSyncJob and moved the reusable methods
to GlusterTaskUtils class. The changes include -
1. Modified the class GlusterTaskUtils as a singleton class
2. Moved reusable code from GlusterTaskSyncJob to GlusterTaskUtils class
3. Modified the dependencies accordingly

Change-Id: I1abecae9389530324154cdc059ee717db0a61715
Signed-off-by: Shubhendu Tripathi <shtripat@redhat.com>