rpm: opendb before rpmverifyscript to avoid null point input

If the command is "rpm -V" and the return value of (headerIsEntry(h, RPMTAG_VERIFYSCRIPT) 
|| headerIsEntry(h, RPMTAG_SANITYCHECK)) located in /lib/verify.c is true, it will call
rpmpsmStage function(rpmVerifyScript->rpmpsmScriptStage->rpmpsmStage) and occur segment
fault because of null point(rpmtsGetRdb(ts) == NULL and rpmtsGetRdb(ts)->db_txn).
So we open rpmdb to avoid bad input when find headerIsEntry true.

Upstream-Status: Pending

Signed-off-by: Zhixiong Chi <zhixiong.chi@windriver.com>
Index: rpm-5.4.14/lib/verify.c
===================================================================
--- rpm-5.4.14.orig/lib/verify.c	2015-07-22 22:09:59.992895355 +0800
+++ rpm-5.4.14/lib/verify.c	2015-08-13 10:20:33.752177906 +0800
@@ -613,6 +613,8 @@
 	{
 	    FD_t fdo = fdDup(STDOUT_FILENO);
 
+	    rpmtsOpenDB(ts, O_RDONLY);            /*Open the DB to avoid null point input in function rpmpsmStage()*/
+
 	    rc = rpmfiSetHeader(fi, h);
 	    if ((rc = rpmVerifyScript(qva, ts, fi, fdo)) != 0)
 		ec += rc;