tests: Clean up build tests

Build tests don't need the 'find' nor 'rm -r' as they don't
create directories.

There is no need to delete the 'test.yml' file in
the output tests.

Consistently use NAME as the name argument

Signed-off-by: Rolf Neugebauer <rolf.neugebauer@docker.com>

test/cases/000_build/100_examples/070_wireguard/test.sh

@@ -8,16 +8,15 @@ set -e
 #. "${RT_LIB}"
 . "${RT_PROJECT_ROOT}/_lib/lib.sh"
 
-IMAGE_NAME=wireguard
+NAME=wireguard
 
 clean_up() {
-	# remove any files, containers, images etc
-	rm -rf ${IMAGE_NAME}*
+	rm -f ${NAME}*
 }
 
 trap clean_up EXIT
 
 # Test code goes here
-moby build "${LINUXKIT_EXAMPLES_DIR}/${IMAGE_NAME}.yml" 
+moby build "${LINUXKIT_EXAMPLES_DIR}/${NAME}.yml" 
 
 exit 0