The various Neutron plugin files need to have unique variables for the
xtrace state as they are sometimes nested more than two levels deep
and MY_XTRACE is getting stomped. This gives each of the neutron_plugin
and neutron_thirdparty include files a unique XTRACE state variable.
I don't think this is a problem with any of the other plugin include
files (yet) so this just handles Neutron for now.
Change-Id: I7c272a48e7974edecaff5f431ff7443dd6622588
e3a9160c0d