Fix intermittent failure in ReplicationAndSnapshotsIntegrationTest

Fix intermittent failure in ReplicationAndSnapshotsIntegrationTest

Verification of the follower's snapshot intermittently fails in
testFirstSnapshot. The problem is that the last applied term/index may
or may not reflect the last log index. The test doesn't expect it to and
most of the time it doesn't but it can, which is perfectly fine. So to
avoid intermittent failures I changed it to just verify the snapshot's
last log term/index which shoild be constant.

Change-Id: I8c6d920bea557dcc2ef25b5d37239fdb94a13b8b
Signed-off-by: Tom Pantelis <tpanteli@brocade.com>