Previously COMPAREANDWRITE was only sending verify instance data which
can cause targets to generate COMMAND ABORTED/NOT ENOUGH UNSOLICITED
DATA errors due to the buffer being obviously too small to contain
verify AND write instance data.
The buffer size check has been modified and compareandwrite tests
updated to pass a larger buffer with interesting write instance data.
Dont call READCAPACITY from every single test.
Remove two arguments from the test signatures and turn them into globals.
remove the ret++ silliness. Tests return 0 : all ok, -2, skipped or -1 : test failed
