qa: don't fail on gather_mount_info() failure

qa: don't fail on gather_mount_info() failure

kernel 5.4 (Ubuntu 20.04) has the following missing commits:

- 5a9e2f5d5590 ceph: add ceph.{cluster_fsid/client_id} vxattrs
- 247b1f19dbeb ceph: add status debugfs file

fs suite relies on these debugfs entries to gather mount information
(client-id, addr/inst) which are required by some tests. In fs suite,
the disto kernel gets overridden by the testing kernel and therefore
even if Ubuntu 20.04 is chosen as the distro, the testing kernel is
installed. However, with smoke suite, the distro kernel is used and
the missing patches causes certain essential information gathering to
fail early on (client-id, etc..) causing the test to not even start
execution. PR #54515 fixes a bug in the client-id fetching path but
isn't complete due to the missing patches - details here:

        https://tracker.ceph.com/issues/63488#note-8

But its essential to have the smoke tests running since those tests
have lately uncovered bugs in the MDS (w/ distro kernels). In order
to benefit from those tests, this change ignores failures when
gathering mount information (which aren't used by the fs relevant
smoke tests). The test (in fs suite) that rely on this piece of
information would fail when run with 20.04 distro kernel (but the
fs suite overrides it with the testing kernel).

Signed-off-by: Venky Shankar <vshankar@redhat.com>
(cherry picked from commit dde5bf4d4ce08f9f0d46b3bb709578561f580179)