ceph/001-003: skip if test_dummy_encryption is enabled

ceph/001-003: skip if test_dummy_encryption is enabled

Some tests on ceph require changing the layout of new files, which
is forbidden when the files are encrypted. Skip these tests if the
test_dummy_encryption mount option is being used.

Generalize the _exclude_scratch_mount_option code and add a new
_exclude_test_mount_option call as well. Call the new function from the
ceph tests that should exclude test_dummy_encryption.

Cc: Luis Henriques <lhenriques@suse.de>
Cc: Eric Biggers <ebiggers@kernel.org>
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: Eric Biggers <ebiggers@google.com>
Reviewed-by: Luis Henriques <lhenriques@suse.de>
Signed-off-by: Eryu Guan <guaneryu@gmail.com>