gluster: Modified to fail remove host if already removed from CLI

Modified to fail remove host if already removed from CLI and not yet
synchronized with UI. Earlier it was not failing in the UI and was
successfully removing the host from UI.

Bug-Url: https://bugzilla.redhat.com/1024183
Change-Id: I1e8c79bcbf9c3dc733641812f505170e369448a1
Signed-off-by: Shubhendu Tripathi <shtripat@redhat.com>