Catch `Exception` even if it isn't thrown, for Kotlin

Kotlin does not observe checked exceptions. https://kotlinlang.org/docs/reference/exceptions.html#checked-exceptions . It [sounds like](https://github.com/grpc/grpc-java/issues/2668#issuecomment-422737424) that that means that even things like `Runnable` can throw checked exceptions.

Lots of code will be broken in such an environment, including lots of Guava. But for improved Kotlin handling we could consider making sure to handle `Exception` catching places we have `RuntimeException` catching if the application may have been called.

It's probably a good idea to confirm the behavior and discuss this problem with Guava folks and come to a unified agreement.

CC @m7onov, @zpencer