vm/netwatcher: ignore error when no external IP present
vm/netwatcher: ignore error when no external IP present

This can be set later - when network in NetVM is connected.

marmarek/qubes-core-admin,woju/qubes-core-admin,marmarek/qubes-core-admin,woju/qubes-core-admin,marmarek/qubes-core-admin,woju/qubes-core-admin,QubesOS/qubes-core-admin,QubesOS/qubes-core-admin,woju/qubes-core-admin,QubesOS/qubes-core-admin