common/rc: Enable _test_mkfs to force a mkfs on a xfs filesystem

common/rc: Enable _test_mkfs to force a mkfs on a xfs filesystem

Calling _test_mkfs on an already initialized xfs FS will fail as the
initialization is not enforced by '-f' argument, unless it's included in
MKFS_OPTIONS.
So, adding 'RECREATE_TEST_DEV=true' to the config file end up being useless
for xfs filesystems.

So, adding the a specific xfs optiong in _test_mkfs using -f argument
makes RECREATE_TEST_DEV actually useful.

Signed-off-by: Carlos Maiolino <cmaiolino@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Zorro Lang <zlang@kernel.org>