meta-agl-core: Improve connman-wait-online usability

Changes:
- Ship connman-wait-online in packagegroup-agl-core-connectivity.
- Add installation of a systemd drop-in configuration file for
  systemd-networkd-wait-online when VIRTUAL_RUNIME_net_manager
  is set to connman that will disable it.  This is required to
  avoid boot hangs if a unit does add a dependency on the
  network-online target.  The approach is not ideal, but it is
  not clear how to avoid systemd-networkd-wait-online getting
  enabled without actually modifying the systemd-networkd unit.

Bug-AGL: SPEC-5082

Change-Id: Id0a1276e35c68ecb6087f89a880fc069594caca4
Signed-off-by: Scott Murray <scott.murray@konsulko.com>
Reviewed-on: https://gerrit.automotivelinux.org/gerrit/c/AGL/meta-agl/+/29697
ci-image-build: Jenkins Job builder account
Tested-by: Jenkins Job builder account
ci-image-boot-test: Jenkins Job builder account
Reviewed-by: Jan-Simon Moeller <jsmoeller@linuxfoundation.org>