First section publish the backup url.
Second section publish the frontend url if available.

Connection url are only usefull for slave instances.

Request has to fail if a connection parameter can not be accessed.

Conflicts:
	software/kvm/software.cfg

Use new recipes in KVM to make instance not raise when no frontend is found,
Don't request slave kvm frontend instance on SAME machine,
Check if frontend is available using a promise

Use new recipes in KVM to make instance not raise when no frontend is found,
Don't request slave kvm frontend instance on SAME machine,
Check if frontend is available using a promise

This reverts commit 35c5c950.

It allows to build libcairo.