TempDir creates a temporary directory that includes the name of the testcase. Panics if there was an I/O problem creating the directory.
Check that loopback Utimens() works as expected. Called by TestLoopbackFileUtimens and TestLoopbackFileSystemUtimens.
path ........ path to the backing file utimensFn ... Utimens() function that acts on the backing file
VerboseTest returns true if the testing framework is run with -v.