Load-balancing cleanup.

The starting point of this patch was allowing a caller (i.e. the metacd_http) to use an iterator different than those specified in the NS configuration. In other words, to thinly wrap the API.

Some code reorganisation took place:
  - function reordering (to be grouped by puposes)
  - obsoletes removals (scored iterators ... meaningless since the score is the weight).
  - functions moved in others modules (checks on the storage class of services, moved into service_info)
  - code factorized (minor container handling, in metautils_containers)

Change-Id: I625fd9413e0fa01d68d085f93160c026b9744c0f
rainx: use new librain interface, factorize code

Dependency updated to redcurrant-librain-0.7.1

Change-Id: I42306a1fd6b81ae2b15b5924596a782c75311081
m2v2,rainx: code cleaning, better memory management

Change-Id: I779c019f19ae11c29ad3e1bc3f185ad9595cc360