Fix broken i18n support

In notification and publisher.rpc module, there are some log messages
don't support i18n, this patch fixes them.

NOTE: rename unused variable from _ to n, because it will overshadow
global _ of gettext.

Change-Id: Ic703fe6536234f4d51a84f4a3b2e04049ec6f3b5
Closes-Bug: #1263711
requirements: drop netaddr

We don't use directly, so there is no need to require it.

Change-Id: I94bbe7fbcfe192ca355ad00a64e0720addc1bb10
Merge "Fix broken i18n support"
Merge "requirements: drop netaddr"
Update ceilometer.conf.sample

Due to python-keystoneclient update.

Change-Id: Ie683d3fbf8086d2be6a2fbe19374b8d31abaf976
Closes-bug: #1268614
Merge "Update ceilometer.conf.sample"