lispd: warn when no petr configured, as per gh-38
lispd: warn when no petr configured, as per gh-38

Warn users of potential consequences that a missing PETR configuration
has.

Lluiso/oor,OpenOverlayRouter/oor,OpenOverlayRouter/oor,Lluiso/oor,OpenOverlayRouter/oor,OpenOverlayRouter/oor,OpenOverlayRouter/oor,Lluiso/oor,Lluiso/oor,OpenOverlayRouter/oor,Lluiso/oor,OpenOverlayRouter/oor