bitbake: main: kill server without queue setup

bitbake: main: kill server without queue setup

Setup of event queue includes registering of UI handler.
This operation can fail when cooker is busy. However, there is
no need in registering UI handler for terminating the server.

Moved the call of connection.terminateServer before setting up
of the event queue. This should make terminating server to work
more reliably as it doesn't depend on setting up the event queue
and registering UI handler anymore.

This should also help Toaster backend to restart bitbake server
and observer without getting "Could not register UI event handler"
errors.

[YOCTO #8776]

(Bitbake rev: 0c5a9349f797d05c282c2ada1893e187e05f0576)

Signed-off-by: Ed Bartosh <ed.bartosh@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>