Kayobe uses a number of virtual environments on the remote hosts for
python dependencies such as shade, python-openstackclient, docker, etc.
By default these are stored in /opt/kayobe/venvs/. Typically we do not
provide version restrictions when installing these packages, so over the
course of time they may become stale and incompatible.

This change installs the latest version of packages allowed by OpenStack
upper constraints.

It also adds a new variable, 'pip_upper_constraints_file', to set the
upper constraints file. The existing variable
'kolla_upper_constraints_file' now defaults to the value of
'pip_upper_constraints_file'.

Change-Id: I8d2956f95bbc44b5a9e88e7569372048a62f12f5
Story: 2005923
Task: 34193