sysctl: Return non-zero if param setting failed

Real usecase:
'sysctl -w user.max_uts_namespaces=2147483648; echo $?'
returns 0 even though it failed with EINVAL

The close_stream() realised there was an issue and printed an
error but didn't change the return value.

Slightly modified merge request.

References:
 procps-ng/procps!76

Signed-off-by: Craig Small <csmall@dropbear.xyz>

sysctl.c

@@ -586,7 +586,7 @@ static int WriteSetting(
 		rc = EXIT_SUCCESS;
             if (close_stream(fp) != 0) {
                 xwarn(_("setting key \"%s\""), path);
-                return rc;
+                return EXIT_FAILURE;
             }
         }
     }