tests/qtest: defer connection

tests/qtest: defer connection

Add an option to defer making the connecting to the monitor and qtest
sockets when calling qtest_init_with_env.  The client makes the connection
later by calling qtest_connect and qtest_qmp_handshake.

Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Link: https://lore.kernel.org/r/1736967650-129648-20-git-send-email-steven.sistare@oracle.com
[plumb capabilities list into qtest_qmp_handshake]
Signed-off-by: Fabiano Rosas <farosas@suse.de>