test-uuid: fix leak

ASAN spotted:
SUMMARY: AddressSanitizer: 74 byte(s) leaked in 2 allocation(s).

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <20161109110210.25925-1-marcandre.lureau@redhat.com>
Reviewed-by: John Snow <jsnow@redhat.com>
Signed-off-by: Fam Zheng <famz@redhat.com>
