client: Fix leading / issue with mds_check_access

client: Fix leading / issue with mds_check_access

The "Client::mds_check_access" expects the target_path without
leading '/' as it eventually calls the "MDSCapMatch::match_path"
which expects the target_path passed to be with out leading '/'
as well.

The single leading '/' was being removed. But absolute path
constructed did have leading '//', so removing all the leading
'/' was necessary.

This causes the clients not to be able to access a particular
path even though it has a rw permission on the specific path.

The patche fixes the leading '//' issue.

Fixes: https://tracker.ceph.com/issues/67212
Signed-off-by: Kotresh HR <khiremat@redhat.com>
(cherry picked from commit 2e2adb2719c40a87d9fc556f5fa492ef6a2580dc)