update default_log_levels set by ceilometer

the current log levels are pretty old. update the current list to
extend current default default_log_level defined in oslo-incubator
and adding in stevedore and keystoneclient levels

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: I239645ef641613a994a48f20c0238e76dc9660f2
Partial-Bug: #1294789
(cherry picked from commit 4d864cef5a2c8ec912bda5b208771d3b7c966934)
Merge "update default_log_levels set by ceilometer" into stable/icehouse