$ sudo systemctl start webdm_snappyd_0.7.service

restults in:
May 29 18:56:03 localhost systemd[1]: Started Snappy WebDM.
May 29 18:56:03 localhost systemd[1]: Starting Snappy WebDM...
May 29 18:56:03 localhost ubuntu-core-launcher[812]: Snappy: 2015/05/29 18:56:03 handlers.go:52: Initializing HTTP handlers...
May 29 18:56:03 localhost ubuntu-core-launcher[812]: Snappy: 2015/05/29 18:56:03 handlers.go:59: decoding problem
May 29 18:56:03 localhost systemd[1]: webdm_snappyd_0.7.service: main process exited, code=exited, status=1/FAILURE
May 29 18:56:03 localhost systemd[1]: Unit webdm_snappyd_0.7.service entered failed state.
May 29 18:56:03 localhost systemd[1]: webdm_snappyd_0.7.service failed.