Reverse TEST_DEV/TEST_DIR replace order

When using ZFS the common dataset names are pool/filesystem and
they are mounted by default at /pool/filesystem.  Since the dataset
name is commonly a substring of the mount point it's important
to always try and patch the longer TEST_DIR pattern first.
Otherwise, tests like 088 and 245 will fair because they will
insert TEST_DEV instead of TEST_DIR.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>