Added per dc / server role breakdown of udp2log packetloss monitoring.

In addition of having a single packetloss metric per udp2log host,
this patchset introduces additional functionality to map a hostname
to it's role and dc and to calculate packetloss per dc / role.

The rolematcher.py determines the role and dc of a hostname; this information is
obtained every 24 hours from noc.wikimedia.org/pybal. Roles include apache,
api, bits, https, mobile, rendering, text, upload.

The interfaces of PacketLossLogtailer.py have not been changed, this changeset
might require some changes in Ganglia as well. A local test of ganglia-logtailer
did work.

Code is pep8 compliant with the exception of some line lengths > 79.

Change-Id: I084c210d996068f213977f2fb942d4a80021be8f
Merge "Added per dc / server role breakdown of udp2log packetloss monitoring." into production