notify-manager: Set urgency

Don't forget to set the urgency when parsing the hints.

Closes: #653 (closed)

Since this changes UI (it sets a fallback icon in case the application sets none let's /cc @bertob):

They'd now use dialog-error-symbolic:

I'm fine with dropping the icon related bit altogether (which was never executed before fixing this issue).

Signed-off-by: Guido Günther guido.gunther@puri.sm