MB-20822: Erase all diverged branch entries correctly in failover table

MB-20822: Erase all diverged branch entries correctly in failover table

When we add an entry in failover table we must erase all the other
entries with higher seqno because they are from a diverged branch.

This commit fixes a bug in the loop that was erasing diverged entires.
In a std::list when we erase an entry, the function returns the
iterator pointing to next element and hence we must be careful not to
double increment it.

Change-Id: I9275fba8057f26e2853a8d7d359f1d01f107f2be
Reviewed-on: http://review.couchbase.org/67481
Reviewed-by: Dave Rigby <daver@couchbase.com>
Well-Formed: buildbot <build@couchbase.com>
Tested-by: buildbot <build@couchbase.com>