Add fclose file descriptor

Coverity scan #742131 (resource leak)

src/zcompile/zcompile.c

@@ -478,6 +478,7 @@ static int zone_open(const char *filename, uint32_t ttl, uint16_t rclass,
 		if (zp_get_in(scanner) == 0) {
 			return 0;
 		}
+		fclose(f);
 	}
 	
 	return 1;