Update SSO URL scheme used in iOS tests.
Update SSO URL scheme used in iOS tests.

The scheme is updated to be different for each tests.
Also adds a key to the Info.plist that is now used on iOS.

BUG=597040

Review-Url: https://codereview.chromium.org/1973963002
Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#393475}

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