hs-clientmanager: Do not store always the client context

hs-clientmanager: Do not store always the client context

This incorrectly assumed that by re-using the same client context we
could gain access to the *current* client's context. But as we have
seen, the fake subscribe mechanism isn't really capable of doing that,
requiring a direct connection from the client to have that in.

Storing the client context make sense to happen only when we can create
it (with a real subscribe verb) and not *re-use* it, and assign it to
other applications. This basically reverts it to the way it was
previously.

Bug-AGL: SPEC-3796

Signed-off-by: Marius Vlad <marius.vlad@collabora.com>
Change-Id: I643dfe91049efa8937c9a8a21eb6fbb366b3fdcc