testimage.bbclass: fix behavior of empty TEST_SUITES
The current behaviour of TEST_SUITES is very confusing.
setting: TEST_SUITES = ""
result: Execute all test cases.
setting: TEST_SUITES = "some_case_not_exist"
result: Error out with 'Empty test suite' message.
The expected behaviour of TEST_SUITES should be:
1. when 'auto' is in it, execute as many test cases as possible
2. when no valid test case is specified, error out and give user message
The first one is implemented by a previous patch.
The second one is fixed in this patch.
Also add debug message to show test cases to be executed. This is
for easier debugging.
Signed-off-by: Chen Qi <Qi.Chen@windriver.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
