aptpkg: apt-add-repository: Use proxy for PPA
aptpkg: apt-add-repository: Use proxy for PPA

Extend proxy support for APT repository handling to PPA addition
via `apt-add-repository`.

Signed-off-by: Alexandru Avadanii <046230ef61405fd997a5cbd7cfcbca66da78c41e@enea.com>

saltstack/salt,saltstack/salt,saltstack/salt,saltstack/salt,saltstack/salt