core: reduce the use of lists

apparently the default object initialization is happening once per
process execution, so must be avoided.

also reduce other usages.

Change-Id: I33078e67c7235f9cdd7e82e1ec2714a5f90426b2
Reported-By: Antoni Segura Puimedon <asegurap@redhat.com>
Signed-off-by: Alon Bar-Lev <alonbl@redhat.com>