In commit d8e09afc ("tests: Convert ivi-shell-app-test.c to use
`weston_ini_setup`") the reference weston.ini for the ivi-shell was
removed, because it is not required by the test anymore.

The reference weston.ini still has value as an example for the ivi-shell
and how the ivi-shell-user-interface has to be configured. Retrieving
this information from the test case is not intuitive. Furthermore, the
file is still referenced by the ivi-shell/README, and the
configuration_data for generating the file was not fully removed.

Bring back the reference weston.ini for the ivi-shell and, while at it, cleanup
the configuration_data() to define only keys that are actually used in
weston.ivi.in.

Signed-off-by: Michael Tretter <m.tretter@pengutronix.de>