Mounts managed by ceph-fuse may get corrupted by e.g. the ceph-fuse process
exiting abruptly, or its parent container being terminated, taking down its
child processes with it.
This commit adds checks to NodeStageVolume and NodePublishVolume procedures
to detect whether a mountpoint in staging_target_path and/or target_path is
corrupted, and remount is performed if corruption is detected.
Signed-off-by: Robert Vasek <robert.vasek@cern.ch>
