Stop reloading contacts when not appropriate.

A recent change had the contacts reloaded every time a new field
is touched. This change not only fixes the problem, but also removes
reloading contacts when changing language, which should make language
switch within LatinIME lighter.

Bug: 5125034
Change-Id: Ia61c4f75a8617113cdce88a2e2c6fdf073146a2d