oeqa/selftest/signing: Fix for hash equivlance server
There were two issues with the test one is that an equivalent hash
could come from the server meaning the signature didn't change when it
should. A uuid string is injected to ensure this does not happen.
If there were multiple warnings the test would also fail as only the
first is prefixed with WARNING. Tweak the string to avoid that failure
mode.
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
