testimage: fallback for empty IMAGE_LINK_NAME

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>

meta/classes/testimage.bbclass

@@ -98,7 +98,7 @@ TESTIMAGELOCK:qemuall = ""
 
 TESTIMAGE_DUMP_DIR ?= "${LOG_DIR}/runtime-hostdump/"
 
-TESTIMAGE_UPDATE_VARS ?= "DL_DIR WORKDIR DEPLOY_DIR"
+TESTIMAGE_UPDATE_VARS ?= "DL_DIR WORKDIR DEPLOY_DIR IMAGE_LINK_NAME"
 
 testimage_dump_target () {
 }
@@ -209,7 +209,7 @@ def testimage_main(d):
     bb.utils.mkdirhier(d.getVar("TEST_LOG_DIR"))
 
     image_name = ("%s/%s" % (d.getVar('DEPLOY_DIR_IMAGE'),
-                             d.getVar('IMAGE_LINK_NAME')))
+                             d.getVar('IMAGE_LINK_NAME') or d.getVar('IMAGE_NAME')))
 
     tdname = "%s.testdata.json" % image_name
     try: