checkpolicy: Fix minor memory leak in checkpolicy

sepol_set_sidtab() is called without calling sepol_sidtab_destroy().
This is not a big deal, since checkpolicy does not run for long, but
it does add noise when checking for other, more important, leaks.

Call sepol_sidtab_destroy() before exiting if not in debug mode.

Signed-off-by: James Carter <jwcart2@tycho.nsa.gov>
diff --git a/checkpolicy/checkpolicy.c b/checkpolicy/checkpolicy.c
index b98bfcd..b744d6a 100644
--- a/checkpolicy/checkpolicy.c
+++ b/checkpolicy/checkpolicy.c
@@ -654,6 +654,7 @@
 
 	if (!debug) {
 		policydb_destroy(&policydb);
+		sepol_sidtab_destroy(&sidtab);
 		exit(0);
 	}