MSIME sample: Make lastClientId non-static

This is a followup for comment in I77bf8c844838f32888004611975cfa316255961b
lastClientId doesn't need to be static as MultiClientInputMethod is single instance.

Bug: 128751901
Test: Manually verified using steps in bug.

Change-Id: I049a5e9966408b1d304e23713fae2c3597d89a5c
2 files changed