First, lldpad doesn't support disabling priority groups (e:0)
without specifying a complete priority group config (which wouldn't
be used anyway, since you're turning it off!).  While this bug is
being fixed upstream, we'll just ignore errors turning off
PG, since if you're using DCB on an interface, you probably want
to use it all the time.

Second, lldpad really wants all PG options on the same configuration
line, not split apart, because it validates the complete package
of options before applying them, regardless of whether or not they
are given in the same command.  Since NM was just emitting all the
options in separate dcbtool invocations anyway, just combine them
all into a single invocation.