This commit conditionally allows the os_nova role to
install build and deploy within a venv. This is the new
default behavior of the role however the functionality
can be disabled.
Implements: blueprint enable-venv-support-within-the-roles
Change-Id: I13cf36058d08934a41b24ccf4f1700321ab00547
Signed-off-by: Kevin Carter <kevin.carter@rackspace.com>