regression tests: convert mount test to use MS_NODEV
The mount regression test passes MS_MANDLOCK to the mount(2) syscall in the test program. When the kernel is configured without CONFIG_MANDATORY_FILE_LOCKING set, attempting to mount a filesystem with this option always fails with EPERM. To fix, convert the test program to use the MS_NODEV option instead.
Nominated for trunk and apparmor branches 2.13 through 2.9.