LU-8080 utils: Replace calls to signal with sigaction

LU-8080 utils: Replace calls to signal with sigaction

The man page for signal (2) states that sigaction should replace
signal for portability. It also states:
"The effects of signal() in a multithreaded process are unspecified."

This patch affects utils/lhsmtool_posix.c for the second reason and
utils/liblustreapi_hsm.c for completeness even though: "The only
portable use of signal() is to set a signal’s disposition to
SIG_DFL or SIG_IGN." (which is what is done in liblustreapi_hsm.c)

Signed-off-by: Quentin Bouget <quentin.bouget.ocre@cea.fr>
Change-Id: Ib247fab937e3aac514f418c7260cdd67fc9e442c
Reviewed-on: http://review.whamcloud.com/19855
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Tested-by: Jenkins
Reviewed-by: John L. Hammond <john.hammond@intel.com>
Reviewed-by: Henri Doreau <henri.doreau@cea.fr>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>