Activate venvs in os-*-config elements source install

  This updates the source install scripts for os-apply collect and
  refresh config elements to activate their virtualenvs before
  performing pip installs,  as without this specifing a manifest for
  e.g. os-apply-config breaks devtest build

Closes-bug: #1305151
Change-Id: I3c42de180f76fb122637c801541f14e50169de89
Merge "Activate venvs in os-*-config elements source install"