Put credman registry-based sessions into PENDING state to start

This makes them act more like remote providers and allows existing
checks regarding when to show the UI work as expected.

Bug: 288913298
Test: manually
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:df8461c4e00de2b44f1eb56136d02dbf2b152d94)
Merged-In: Ia12cef3031c41206ab74616154c75fd415b31a0e
Change-Id: Ia12cef3031c41206ab74616154c75fd415b31a0e