Fix Swift config for Ceilometer usage

Ceilometer filter was previously removed from the Swift
configuration to avoid useless Ceilometer logs in the Swift
ones. This was fixed by setting only warning log level for
this Ceilometer part of the pipeline to keep only important
ones.

Change-Id: I8c41355bb98dbf3bb59ec792221b05ea936086b7
Partial-Bug: #1294789
Add pre-install phase for extras.d plugins

An additional call hook for the extras.d plugins that is called before
any service installation occurs turns out to be needed by Ceph and
useful for other plugins.

This is called between the installation of the system packages listed
as prerequisites and the installation of the actual services.

Change-Id: Id723bdc7542182d2b2eff40c0dc0127307f094c5
Merge "Fix Swift config for Ceilometer usage"
Merge "Add pre-install phase for extras.d plugins"
Merge branch 'master' of https://github.com/openstack-dev/devstack