xwayland: initiate one EI context per client
Previously, Xwayland itself would open a connection with EI on behalf of its clients. While this work, this is a all-or-nothing solution as neither libei nor the user can identify the actual X11 client tryign to use XTEST.
To differentiate between X11 clients using XTEST, initiate a libEI context for each client and use the actual client name, from its command line.
Signed-off-by: Olivier Fourdan ofourdan@redhat.com