setproctitle: fix ununitialised variable

Reported-by: Coverity (CID-1573333)

Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Ameer Hamza <ahamza@ixsystems.com>
Signed-off-by: Rob Norris <robn@despairlabs.com>
Closes #15649

lib/libzutil/os/linux/zutil_setproctitle.c

@@ -88,7 +88,7 @@ spt_copyenv(int envc, char *envp[])
 	char **envcopy;
 	char *eq;
 	int envsize;
-	int i, error;
+	int i, error = 0;
 
 	if (environ != envp)
 		return (0);