controllers/masterimage.py: Make testimage kernel naming pattern universal
YB: #6254
The QemuTargetControl class does not specify any kernel naming but the runqemu script it uses uses the " KERNEL_IMAGETYPE + MACHINE + '.bin' " naming scheme.
Modifying the other major target controller class, MasterImageHardwareTarget, to use the same kernel naming scheme.
This is usefull also to outside scripts that want to anticipate the kernel file name for all target controllers.
Signed-off-by: Corneliu Stoicescu <corneliux.stoicescu@intel.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
