log: Fix commit headers and -p flag

We weren't flushing the commit message before the diff output, which
meant the headers and message showed randomly interleaved with the
diff rather than immediately before.

Change-Id: I6cefab8d40e9d40c937e9deb12911188fec41b26
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

org.eclipse.jgit.pgm/src/org/eclipse/jgit/pgm/Log.java

@@ -234,10 +234,10 @@ class Log extends RevWalkTextBuiltin {
 		if (showNameAndStatusOnly)
 			Diff.nameStatus(out, diffFmt.scan(a, b));
 		else {
+			out.flush();
 			diffFmt.format(a, b);
 			diffFmt.flush();
 		}
 		out.println();
-		out.flush();
 	}
 }