connman: Depend on xuser-account unconditionally

connman: Depend on xuser-account unconditionally

This means dragging in xuser-account even when it's not used but
that's a lesser evil than the recipe depending on machine specific
settings.

This also prevents a warning on connman service startup when
ROOTLESS_X is not set:
  Unknown username "xuser" in message bus

[YOCTO #8005]

Signed-off-by: Jussi Kukkonen <jussi.kukkonen@intel.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>