openvpn: fix INITSCRIPT overwrites
openvpn: fix INITSCRIPT overwrites

The upstream openvpn_2.5.2.bb recipe in meta-OE implements its own
update-rc.d class assignments, and it uses the `_${PN}` overrride
syntax.  As a result, any generic variable assignments made in the
meta-nilrt bbappend are deprioritized vs. the values from meta-OE, and
they become ineffective.

Update the meta-nilrt variable assignments to use `_${PN}` specifically,
so that BB prefers them over meta-OE.

Signed-off-by: Alex Stewart <04cdb2793e4fb0120cc30d1c823099f3862701f4@ni.com>

ni/meta-nilrt,ni/meta-nilrt,ni/meta-nilrt,ni/meta-nilrt,ni/meta-nilrt