mdadm: Replace obsolete usleep with nanosleep

According to POSIX.1-2001, usleep is considered obsolete.
Replace it with a wrapper that uses nanosleep, as recommended in man.
Add handy macros for conversions between msec, usec and nsec.

Signed-off-by: Mateusz Grzonka <mateusz.grzonka@intel.com>
Signed-off-by: Jes Sorensen <jsorensen@fb.com>
8 files changed