core: bugfix in correlationId machanism

In commit http://gerrit.ovirt.org/#/c/15795/16 a bug was
introduced causing certain commands to not log their
correlationId (see bug description comment). correlationId
must be written on thread local to get logged.

Change-Id: Ie416d6f48f6209985f3cae36566a475e7fa90963
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=987915
Signed-off-by: Mooli Tayer <mtayer@redhat.com>