Move keystone pip package from a constraint to a requirement

This is necessary to support the new pip resolver.

Depends-On: I9be6bbf4a29a4da2ddf96dc0336bc2a7d8ec9281
Depends-On: I49c75dd11d6c4e8d37fe013b7ffdfd56ff193fcd
Change-Id: I599f9de82a6350599444096e98a0e25a417e18ef

defaults/main.yml

@@ -42,7 +42,6 @@ keystone_git_repo: https://opendev.org/openstack/keystone
 keystone_git_install_branch: master
 keystone_upper_constraints_url: "{{ requirements_git_url | default('https://releases.openstack.org/constraints/upper/' ~ requirements_git_install_branch | default('master')) }}"
 keystone_git_constraints:
-  - "git+{{ keystone_git_repo }}@{{ keystone_git_install_branch }}#egg=keystone"
   - "--constraint {{ keystone_upper_constraints_url }}"
 
 keystone_pip_install_args: "{{ pip_install_options | default('') }}"
@@ -489,7 +488,7 @@ keystone_ceilometer_enabled: false
 
 # Common pip packages
 keystone_pip_packages:
-  - keystone
+  - "git+{{ keystone_git_repo }}@{{ keystone_git_install_branch }}#egg=keystone"
   - ldappool
   - osprofiler
   - PyMySQL