doesn't call pam_acct_mgmt()

[jnahmias]

Per the example program at http://www.linux-pam.org/Linux-PAM-html/adg-example.html
the authenticate() method should call pam_acct_mgmt() after calling pam_authenticate() [and before calling pam_setcred()].

Without this call, an account could be expired and still be successfully authenticated.

[FirefighterBlu3]

very good suggestion, applied PR from @okin which addresses this