[Core] try/catch around the entire method to report unhandled exceptions.

https://bugzilla.xamarin.com/show_bug.cgi?id=17307
[Core] Really make sure no exceptions leak from our logging methods

Ensure there are try/catches in the appropriate places to (hopefully)
ensure we never end up in a situation where we are stuck in an exception
reporting loop.
Merge pull request #549 from mono/logging-service-try-catch-entire-method

[Core] try/catch around the entire method to report unhandled exceptions