blacklist: Fix minor memory leak in configuration parsing error case

Ordinarily, the continue clause of the for-loop would free 'line.'  In this
case we instead return early, missing the free.  Add an explicit free to
avoid the leak.

Reported by:	Coverity
Sponsored by:	Dell EMC Isilon

contrib/blacklist/bin/conf.c

@@ -1119,6 +1119,7 @@ conf_parse(const char *f)
 				confset_free(&lc);
 				confset_free(&rc);
 				fclose(fp);
+				free(line);
 				return;
 			}
 		}