Caches from 'ext4_groupinfo_caches' may be in use by other mounts,
which have already existed.  So, it is incorrect to destroy them when
newly requested mount fails.

Found by Linux File System Verification project (linuxtesting.org).
Signed-off-by: Andrey Tsyvarev <tsyvarev@ispras.ru>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Reviewed-by: Lukas Czerner <lczerner@redhat.com>