PPP: Replace no_terminate_on_pause flag with terminate_on_pause flag

PPP: Replace no_terminate_on_pause flag with terminate_on_pause flag

We know of two real-world PPP-based VPNs that require us *not* to TERMINATE
at the PPP layer if we will want to subsequently resume a connection.  We
don't know of any real-world PPP-based VPNs that *do* want us to TERMINATE
at the PPP layer in this case; in fact, any server that *requires* this
would be unable to resume inadvertently dropped connections.

Replace the no_terminate_on_pause flag with a terminate_on_pause flag, in
order to reduce boilerplate and use the more plausible behavior as the
default.

Signed-off-by: Daniel Lenski <dlenski@gmail.com>