Fix failing test

DefaultForWritingSystem_OldPalasoKeymanKeyboard() failed on my
machine because I already had an IPA Unicode 1.1.1 keyboard
installed. This change modifies the test to use the existing
IPA keyboard; if none exists then it "installs" a new one.

Change-Id: I11b0d2e5266a8fb0165833cda047b0b7c3946309
Improve initial value of ActiveKeyboard

This change modifies ActiveKeyboard so that it returns the keyboard
for the currently active input language even before we switched
keyboards. Previously we initially returned the null-keyboard until
our code switched the keyboard at least once.

Change-Id: I29c4c3267f345e8af36544a8b899c75b60af9784