LU-4839 utils: fix bandwidth ctl in lhsmtool

LU-4839 utils: fix bandwidth ctl in lhsmtool

Use nanosleep for bandwidth control because usleep fails
for times of a second or longer (usleep(2) EINVAL return value). Add
loop in case sleep is woken by signal.

This is a backport to b2_5 of
Lustre-change: http://review.whamcloud.com/#/c/12093/
Lustre-commit: f74ace3919d60dc05664caa32f5a79abc3a2fe91

Signed-off-by: Nathaniel Clark <nathaniel.l.clark@intel.com>
Change-Id: Ib58676b878678eb399bf58bb9873d8fb411b3316
Reviewed-by: John L. Hammond <john.hammond@intel.com>
Reviewed-by: James Nunez <james.a.nunez@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>
Reviewed-on: http://review.whamcloud.com/12405
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>