Replaced shlex with dockerfile/shell package

integration_tests/dockerfiles/Dockerfile_test_env

@@ -13,3 +13,7 @@ ENV test2='a"b"c'
 ENV test3=a\ b name2=b\ c
 ENV test4="a\"b"
 ENV test5='a\"b'
+ENV test6="a\'b"
+ENV atomic=one
+ENV atomic=two newatomic=$atomic
+ENV newenv=$doesntexist/newenv

integration_tests/dockerfiles/test_env.yaml

@@ -31,3 +31,11 @@ metadataTest:
       value: a"b
     - key: test5
       value: a\"b
+    - key: test6
+      value: a\'b
+    - key: atomic
+      value: two
+    - key: newatomic
+      value: one
+    - key: newenv
+      value: /newenv