Change to an explicit check for boards which are offlining, reserved or  already offline to allow job submission as long as the boards are not retired. Clarify exception message.
Change to an explicit check for boards which are offlining, reserved or 
already offline to allow job submission as long as the boards
are not retired. Clarify exception message.


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