client: retry remount on dcache invalidation failure

client: retry remount on dcache invalidation failure

For some (unknown) reason, there have been reports of
ceph-fuse crash due to failure is remounting at the
time of invalidating kernel dentry cache. This issue
is not also reproducible yet.

Therefore, as suggested by Patrick and Zheng, for a
temporary workaround, client would ignore the failure
as the invalidation would be retried again. There is
a max cap on the number of consecutive remount failures
after which client would abort.

Fixes: http://tracker.ceph.com/issues/35931
Signed-off-by: Venky Shankar <vshankar@redhat.com>
(cherry picked from commit d1471f070cd1ad9c0f773e00d2552161d1ad5955)

 Conflicts:
	src/client/Client.cc
	src/client/Client.h
	src/common/options.cc