Add fflush for the case the log is redirected to the buffered file.

Without this patch it have not been obvious, why the application
waits on the stdin as the prompt might be still buffered in memory.

WHATS_NEW

@@ -1,5 +1,6 @@
 Version 2.02.55 -
 ===================================
+  Flush stdout after yes/no prompt.
   Update vgsplit and vgcreate to use vg_set_clustered.
   Add vg_mda_count and vg_set_clustered library function.
   Add more vgcreate and vgsplit nightly tests.

lib/display/display.c

@@ -824,6 +824,7 @@ char yes_no_prompt(const char *prompt, ...)
 			va_start(ap, prompt);
 			vprintf(prompt, ap);
 			va_end(ap);
+			fflush(stdout);
 		}
 
 		if ((c = getchar()) == EOF) {