Deflake the meta_arg_test by setting a specific timestamp in touch. (#498)

This works around mtime-precision issues that cause us to differ from docker-built images
when the touch command executes too quickly to modify the mtime.

Also one fix in the .travis.yml beacuse something appears to have changed in their default
go installation.

.travis.yml

@@ -2,7 +2,7 @@ language: go
 os: linux
 
 go:
-  - 1.10.x
+  - "1.10"
 go_import_path: github.com/GoogleContainerTools/kaniko
 
 script:

integration/dockerfiles/Dockerfile_test_meta_arg

@@ -14,4 +14,5 @@ FROM ${REGISTRY}/${REPO}/debian9
 COPY --from=stage1 /hello /tmp
 
 # /tmp/hey should not get created without the ARG statement
-RUN touch /tmp/${WORD2}
+# Use -d 0 to force a time change because of stat resolution
+RUN touch -d 0 /tmp/${WORD2}