memcached: use nrpe when binding to localhost

Binding to localhost currently means the check from the nagios server is
provisioned, but failing; this happens specifically on holmium (blog).

Modify the code to provision an nrpe check instead, but only if the bind
address is 127.0.0.1. Keep remote checks for the non-localhost case, as
it's better to not rely to nrpe for checking in those (e.g.  for our mc
cluster).

Since this was made specifically for holmium, also add an "include nrpe"
in the blog class.

RT: 6368
Change-Id: I45f5f9240f74b608cffbae2762987b8e1f88ccbb