Check values for EC2.
Check values for EC2.

- Add multiple check to methods to make sure we have a proper
  tenant_id/user_id/credentials.
- Fixes bug 958135.

Change-Id: I4dd171e3db32d6ebdc70bb1a83492c8ecd09c21c

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