rename resource nitb_iface to ip_address

I would like to use the IP addresses also for OsmoBSC processes, so it is more
than clear now that 'nitb_iface' was the wrong naming choice.

The only distinction we may need in the future is public versus loopback
interface. To add that, we may add a trait to the 'ip_address' resource
like:

  ip_address:
  - addr: 10.42.42.1
    type: public
  - addr: 127.0.0.1
    type: loopback

This way we can substitute public vs loopback addresses flexibly (e.g. using
scenarios).

Change-Id: I3ad583ae7a33f7a7bb56fe78a125f73c56a0e860
diff --git a/suites/debug/suite.conf b/suites/debug/suite.conf
index 04959b8..adfc161 100644
--- a/suites/debug/suite.conf
+++ b/suites/debug/suite.conf
@@ -1,5 +1,5 @@
 resources:
-  nitb_iface:
+  ip_address:
   - times: 1
   bts:
   - times: 1