Fix returns_placeholder to prevent it from getting wrapped as a composite_step.
Fix returns_placeholder to prevent it from getting wrapped as a composite_step.

R=luqui@chromium.org
BUG=

Review URL: https://codereview.chromium.org/1111093002

git-svn-id: 239fca9b83025a0b6f823aeeca02ba5be3d9fd76@295050 0039d316-1c4b-4281-b951-d872f2087c98

shishkander/recipes-py,shishkander/recipes-py,luci/recipes-py,luci/recipes-py