Improve the validation message when a role is not found in every multinode action
Improve the validation message when a role is not found in every
multinode action

Change-Id: I55c0b0a29c05dd352aee10bc5f1e895d62ce0b77

Linaro/lava-server,Linaro/lava-server,Linaro/lava-server,Linaro/lava-server