jsonrpc: Json processing issues fixed

Number of issues fixed:
- Default value was missing in SP.disconnect
- Host.setupNetworks and Image.download was returning True where as it
should return information according to schema
- Bridge.py did not processed order of optional parameters properly.
For fencing flow second optional parameter is ued which caused the
issue. Fix provide default value for any optional parameters in between.

Change-Id: I33094f3e761c616141f60c190f7deaec08fe1f08
Signed-off-by: pkliczewski <piotr.kliczewski@gmail.com>
Reviewed-on: http://gerrit.ovirt.org/28505
Reviewed-by: Dan Kenigsberg <danken@redhat.com>