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.

that is needed in stable/icehouse to allow swift+ceilometer
in devstack and devstack gate (otherwise grenade job, that is
using stable/icehouse devstack, won't pass the gate)

Change-Id: I8c41355bb98dbf3bb59ec792221b05ea936086b7
Partial-Bug: #1294789
(cherry picked from commit eedfdee060b17d38b14628b7e706967cb15a35af)
Merge "Fix Swift config for Ceilometer usage" into stable/icehouse