Ensure all the method requests are handled by didcot

As didcot and barkway are on demand services, there might
be chances where didcot tries to show selection popup but
proxy for barkway is not yet created. So queue the requests
and handle the requests after getting the proxy if any.

Apertis: https://phabricator.apertis.org/T3757



Signed-off-by: Rohan Madgula <Rohan.Madgula@in.bosch.com>
Reviewed-by: Frédéric Dalleau <frederic.dalleau@collabora.com>
Differential Revision: https://phabricator.apertis.org/D6319