Store parsed query parameters directly in the virURIPtr struct

Store parsed query parameters directly in the virURIPtr struct

Avoid the need for each driver to parse query parameters itself
by storing them directly in the virURIPtr struct. The parsing
code is a copy of that from src/util/qparams.c  The latter will
be removed in a later patch

* src/util/viruri.h: Add query params to virURIPtr
* src/util/viruri.c: Parse query parameters when creating virURIPtr
* tests/viruritest.c: Expand test to cover params

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>