package_to_container: fix package name nit

repo syncing from scratch and trying to emerge libcontainer_overrides
fails to find ebuilds, this fixes that by using the full package name.

BUG=chromium:624334
TEST=None

Change-Id: Icbcbbda8fbc0c0ddb47afadb73314f2e12a4e712
Reviewed-on: https://chromium-review.googlesource.com/360244
Commit-Ready: Ashish Gaurav <ashishgaurav@chromium.org>
Tested-by: Ashish Gaurav <ashishgaurav@chromium.org>
Reviewed-by: Dylan Reid <dgreid@chromium.org>
1 file changed