Unpin pam dependency version
Unpin pam dependency version

Fixes bug #1133240

keystone has always pinned the pam dependency to 0.1.4

  pam>=0.1.4

this version was released in November 2009 and there hasn't been a
release since. I can't even find a version control repo for the
project.

There's no particular reason to expect a future version would break us
and, indeed, we want to find out about it if it happens.

Change-Id: I2becf47c9d2566e2c3496ae15ca886b737006a92

derekchiang/keystone,ntt-sic/keystone,JioCloud/keystone,rickerc/keystone_audit,derekchiang/keystone,MaheshIBM/keystone,openstack/keystone,rajalokan/keystone,citrix-openstack-build/keystone,jamielennox/keystone,townbull/keystone-dtrust,klmitch/keystone,jumpstarter-io/keystone,rodrigods/keystone,nuxeh/keystone,dstanek/keystone,cloudbau/keystone,himanshu-setia/keystone,kwss/keystone,dsiddharth/access-keys,nuxeh/keystone,reeshupatel/demo,ilay09/keystone,roopali8/keystone,takeshineshiro/keystone,klmitch/keystone,promptworks/keystone,rickerc/keystone_audit,mahak/keystone,takeshineshiro/keystone,jumpstarter-io/keystone,cernops/keystone,promptworks/keystone,ajayaa/keystone,rushiagr/keystone,rajalokan/keystone,ntt-sic/keystone,citrix-openstack-build/keystone,himanshu-setia/keystone,vivekdhayaal/keystone,blueboxgroup/keystone,maestro-hybrid-cloud/keystone,jonnary/keystone,dsiddharth/access-keys,JioCloud/keystone,cbrucks/Federated_Keystone,roopali8/keystone,jonnary/keystone,vivekdhayaal/keystone,townbull/keystone-dtrust,MaheshIBM/keystone,cbrucks/Federated_Keystone,blueboxgroup/keystone,idjaw/keystone,dstanek/keystone,ging/keystone,maestro-hybrid-cloud/keystone,rushiagr/keystone,idjaw/keystone,promptworks/keystone,ilay09/keystone,cloudbau/keystone,kwss/keystone,UTSA-ICS/keystone-kerberos,kwss/keystone,openstack/keystone,UTSA-ICS/keystone-kerberos,dsiddharth/access-keys,jamielennox/keystone,dims/keystone,derekchiang/keystone,rajalokan/keystone,openstack/keystone,mahak/keystone,ntt-sic/keystone,rushiagr/keystone,rodrigods/keystone,rickerc/keystone_audit,cbrucks/Federated_Keystone,dims/keystone,ilay09/keystone,cernops/keystone,citrix-openstack-build/keystone,ajayaa/keystone,vivekdhayaal/keystone,mahak/keystone,reeshupatel/demo,cloudbau/keystone,jumpstarter-io/keystone,dstanek/keystone,nuxeh/keystone,reeshupatel/demo,townbull/keystone-dtrust,ging/keystone