iotests: skip FUSE tests when FUSE is not usable
file-io-error, fuse-allow-other and fuse-mmap-shared skip only when FUSE is not compiled in. When FUSE is built in but unusable at run time (no /dev/fuse access, fusermount lacking permissions), the export fails to mount with "Failed to mount FUSE session to export" and the tests report a spurious failure instead of skipping, like NBD tests already do for missing NBD support. Add _notrun_on_fuse_error() to common.rc and use it in the shell tests. fuse-mmap-shared is Python, so it gets an equivalent inline check. Signed-off-by: Denis V. Lunev <den@openvz.org> CC: Kevin Wolf <kwolf@redhat.com> CC: Hanna Reitz <hreitz@redhat.com> Message-ID: <20260715103451.1930909-3-den@openvz.org> Reviewed-by: Daniel P. Berrangé <berrange@redhat.com> Reviewed-by: Kevin Wolf <kwolf@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>