Allow for trailing whitespace when sanitizing the micro-bosh manifest

The YAML produced on the local machine can contain trailing whitespace
in lines, e.g. "properties: !map:Settingslogic ".  Earlier versions of
the sanitization regexp matched such cases, but it got changed to require
an end-of-line in 5b73522cd78e125c.

This version restores the old matching behavior, while still eliminating
preceding whitespace.