check: try reloading modules

Optionally reload the module between each test to try to pinpoint slab
cache errors and whatnot.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Eryu Guan <guaneryu@gmail.com>
Signed-off-by: Eryu Guan <guaneryu@gmail.com>

README

@@ -106,6 +106,9 @@ Preparing system for tests:
              - set USE_KMEMLEAK=yes to scan for memory leaks in the kernel
                after every test, if the kernel supports kmemleak.
              - set KEEP_DMESG=yes to keep dmesg log after test
+             - Set TEST_FS_MODULE_RELOAD=1 to unload the module and reload
+               it between test invocations.  This assumes that the name of
+               the module is the same as FSTYP.
 
         - or add a case to the switch in common/config assigning
           these variables based on the hostname of your test