libxl: Move "qmp_initializations" to libxl_dm

libxl: Move "qmp_initializations" to libxl_dm

libxl__qmp_initializations is part of the device domain startup, it
queries information about the newly spawned QEMU and do some
post-startup configuration. So the function call doesn't belong to the
general domain creation, but only to the device model part of the
process, thus the call belong to libxl_dm and libxl__dm_spawn_state's
machinery.

We move the call ahead of a follow-up patch which going to "inline"
libxl__qmp_initializations.

Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>