if IMAGE_LINK_NAME is set empty to disable the symlinking
for image artifacts in deploy, testimage fails, as the path assembly
is incorrect.
In that case fallback to IMAGE_NAME

(From OE-Core rev: c7a4e7e294992acc589c62adcaf6cd32659f2f9b)

(From OE-Core rev: 5b4c7a39f7a99d5c98eab3aaf693f4d3000c7ac1)

Signed-off-by: Konrad Weihmann <kweihmann@outlook.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
Signed-off-by: Steve Sakoman <steve@sakoman.com>