Pass flag to indicate multiple users on device

When creating a new account, some informational text changes when
more than one user exists on the device. Because GLS is built with
the SDK and because there is no public API to indicate this state,
a flag is added to the bundle passed to the AccountManager, which
then funnels down to GLS.

Bug: 7255673
Change-Id: Ida2aa5f70ab308958de510a95194463c2a089182