ping: Flush stdout after printing initial status

MFC after:	1 week
Reviewed by:	markj
Differential Revision:	https://reviews.freebsd.org/D57765

sbin/ping/ping.c

@@ -829,7 +829,6 @@ ping(int argc, char *const *argv)
 			    sweepmin, sweepmax);
 		else
 			(void)printf(": %d data bytes\n", datalen);
-
 	} else {
 		if (sweepmax)
 			(void)printf("PING %s: (%d ... %d) data bytes\n",
@@ -837,6 +836,7 @@ ping(int argc, char *const *argv)
 		else
 			(void)printf("PING %s: %d data bytes\n", hostname, datalen);
 	}
+	(void)fflush(stdout);
 
 	/*
 	 * Use sigaction() instead of signal() to get unambiguous semantics,

sbin/ping/ping6.c

@@ -1114,6 +1114,7 @@ ping6(int argc, char *argv[])
 	    (unsigned long)(pingerlen() - 8));
 	printf("%s --> ", pr_addr((struct sockaddr *)&src, sizeof(src)));
 	printf("%s\n", pr_addr((struct sockaddr *)&dst, sizeof(dst)));
+	fflush(stdout);
 
 	if (preload == 0)
 		pinger();