qa: fix a few issues detected by coverity

sys/src/kern/boot/bootip.c

@@ -39,6 +39,8 @@ configip(int bargc, char **bargv, int needfs)
 	memmove(arg, bargv, bargc * sizeof(char*));
 	arg[bargc] = 0;
 
+	buf[0] = 0; /* no default for outin */
+
 print("ipconfig...");
 	argc = bargc;
 	argv = arg;