wt-status: release strbuf after use in wt_longstatus_print_tracking()

If format_tracking_info() returns 0, then it didn't touch its strbuf
parameter, so it's OK to exit early in that case.  Clean up sb in the
other case.

Signed-off-by: Rene Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

wt-status.c

@@ -1026,6 +1026,7 @@ static void wt_longstatus_print_tracking(struct wt_status *s)
 				 comment_line_char);
 	else
 		fputs("\n", s->fp);
+	strbuf_release(&sb);
 }
 
 static int has_unmerged(struct wt_status *s)