ceilometer spamming syslog

regression in code which causes ceilometer to spam syslog. this
patch explicitly configures log_level in ceilometer swift
middleware as we no longer rely on swift middleware logic to
configure it.

Change-Id: I248040cb1d842cf89ed32ef28d8575012d36e08f
Closes-Bug: #1367880
Merge "ceilometer spamming syslog"