Fix for provisioning_devices failure on user builds.
provisioning_devices tries to use "adb shell su" to set content
settings. However, "su" is not available for user builds and
thus provisioning_devices fails for devices with user builds.
This CL fixes this failure by only setting the content settings
when the device has a userdebug build.
BUG=385789
Review URL: https://codereview.chromium.org/
344233005
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@279873 0039d316-1c4b-4281-b951-d872f2087c98