tests: remove unused temporary files for MMP tests

tests: remove unused temporary files for MMP tests

The MMP tests need to be run on a real disk instead of tmpfs, since
the MMP block access is using O_DIRECT.  As such, they create their
own test files in the local testing directory instead of using the
temporary file created in /tmp by the test_one script.  Delete the
tempfs file before clobbering TMPFILE, otherwise it will leave the
unused file in /tmp after the test is completed.

Signed-off-by: Andreas Dilger <adilger@dilger.ca>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>