Description of problem:
validate-sat-cert.pl ignores the fact the PGP public key expired and successfully validates the entitlements certificate

Version-Release number of selected component (if applicable):
sat560

How reproducible:
always

Steps to Reproduce:
1. Our current pgp public key in webapp-keyring.gpg expires at: 2014-02-15

$ gpg --list-keys --no-default-keyring --keyring spacewalk/config/etc/webapp-keyring.gpg
spacewalk/config/etc/webapp-keyring.gpg
---------------------------------------
pub   1024D/06947932 2004-02-18 [expires: 2014-02-15]
uid                  Red Hat Network (Satellite Certificate Signing Key) <rhn-feedback>
sub   2048g/C71F2F5C 2004-02-18 [expires: 2014-02-15]

Let's set the current date after this date ...
# date -s 'Aug 01 2015'
Sat Aug  1 00:00:00 EDT 2015

2. validate current entitlements certificate
# validate-sat-cert --keyring=/etc/webapp-keyring.gpg /etc/sysconfig/rhn/rhn-entitlement-cert.xml && echo $?
gpg: Signature made Fri 07 Jun 2013 11:40:36 AM EDT using DSA key ID 06947932
gpg: Good signature from "Red Hat Network (Satellite Certificate Signing Key) <rhn-feedback>"
gpg: Note: This key has expired!
Primary key fingerprint: 3E7B 88A8 BD63 A59F FCD6  8B58 9E72 9DAF 0694 7932
Certificate validated successfully.
0

Actual results:
See the note - "gpg: Note: This key has expired!"
And return value: 0

Expected results:
The certificate actually should not be successfully validated, the validation should fail.