Allow showing when control target is IME fallback

When we need to make the IME fallback the control target, we also
need to allow showing the IME as the existing check doesn't pass.

Bug: 111084606
Test: MultiDisplaySystemDecorationTests.testCrossDisplayBasicImeOperations
Test: MultiDisplaySecurityTests.testNoInputConnectionForUntrustedVirtualDisplay
Change-Id: Ibbf21a8da2e523fce1703b80b1cba45c0989eecf