Attempt fixing FrameworksImeTests

The current suspicion is that SimpleTestIme isn't considered installed yet
by the time that `am instrument` is invoked, and then fails with a signature
mismatch.

To work around that, install the SimpleTestIme first.

Change-Id: Ic3722164c27f2f547b39afd418a70fbe3e9442bf
Fixes: 311042427