engine: avoid passing userId in User queries

Motivation: in the included queries (user queries), a user id
is passed in parameters.
In user query there is no point in passing userId (it can be taken
from session in server side).
Removed user id paramerters classes, query base class, related tests, and
references both in UI and REST.

Note: although there can be a use case for fetching other user vm/pools, it
can be revisited upon request (currently there is no use for that).

Change-Id: I06bec1770adbc6dce07baae8e5fc7f163b39fc52
Signed-off-by: Gilad Chaplik <gchaplik@redhat.com>