Tune up mod_wsgi settings in example configuration

Explicitly set mod-wsgi process-group to ceilometer-api in sample
This gives the process a good name in process listings.

Set number of process and threads to two and ten respectively. This
represents a reasonable setting to achieve moderate levels of
concurrency.

Change-Id: Iada6126cb525d597cc385c2d63e6228ef08d55a7
Use oslo.msg retry API in rpc publisher

This patch removes the ceilometer hack around rabbitmq configuration
to use the oslo.messaging API to retry rpc connection.

Closes bug #1244698
Co-Authored-By: Ala Rezmerita <ala.rezmerita@cloudwatt.com>

Change-Id: I162f2ce7ba7f6644d995dfeef8b0ef5e2727c226
Merge "Use oslo.msg retry API in rpc publisher"
Merge "Tune up mod_wsgi settings in example configuration"