The \0 after error code prevent logging error message which is after it.
This change clobber qubesd-query exit code with tr exit code (mostly 0),
but this is a good thing - failing qubes-suspend service does not
prevent the suspend, but do prevent the stop hooks being called, which
for example breaks time synchronization or may leave some domains
paused.
QubesOS/qubes-issues#3489
Host suspend notification may be useful not only to driver domains. For
example Whonix needs to resync time after suspend.
Thanks @adrelanos for help.
FixesQubesOS/qubes-issues#1663
