xl2tpd: modify recipes to avoid forced internet access

We should always specify a commit id for git SRCREV or
we will try to access the upstream repo when fetching.

In addition, if our PV is just "git" we will access upstream
when doing archiver functions, so we should specify PV for
xyz_git.bb recipes.

Signed-off-by: Joe Slater <jslater@windriver.com>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>
Signed-off-by: Joe MacDonald <joe_macdonald@mentor.com>