Add EC2 credentials CRUD

ec2 credentials: create, delete, list, show

Change-Id: I82ff84ed433cd9a2da9534bf5f584a2e1a3fe68c
Sync install_venv_common from oslo

Change-Id: I0a57c658e0f89d13963862013793e12ae208c05b
Merge "Add EC2 credentials CRUD"
Merge "Sync install_venv_common from oslo"