qa/cephfs: add session_timeout option support

qa/cephfs: add session_timeout option support

When the mds revoking the Fwbl caps, the clients need to flush
the dirty data back to the OSDs, but the flush may make the OSDs
to be overloaded and slow, which may take more than 60 seconds to
finish. Then the MDS daemons will report the WRN messages.

For the teuthology test cases, let's just increase the timeout
value to make it work.

Fixes: https://tracker.ceph.com/issues/47565
Signed-off-by: Xiubo Li <xiubli@redhat.com>
(cherry picked from commit 0422673b6150df851a4ea1662637a77585cde52d)