Normalize sanlock exit code
Normalize sanlock exit code, so it exit with EXIT_FAILURE on all
failures.
Previously sanlock terminated with exit code 255 if lockfile() failed,
145 if client cannot connect to the daemon, or any other number
depending on return value of failing function.
Exit codes above 128 should be returned only when the process was
terminated by signal (typically 128 + signo), and using them for other
errors may confuse applications managing sanlock.
Since sanlock exit code is not documented, this change should not break
any user code.
Signed-off-by: Nir Soffer <nsoffer@redhat.com>