updatehub-image-tasks.bbclass: Ensure all uhu variables are available
updatehub-image-tasks.bbclass: Ensure all uhu variables are available

The uhu variables (related to image signing and access to the server)
should be available for all uhu tasks.

Signed-off-by: Otavio Salvador <1d31b11c1b92bf5d043d36edfe7174db39a6b891@ossystems.com.br>

UpdateHub/meta-updatehub,UpdateHub/meta-updatehub,UpdateHub/meta-updatehub,fbertux/meta-updatehub,fbertux/meta-updatehub,fbertux/meta-updatehub