The caller of FontFamily::hasVariationSelector needs to acquire the
lock before calling it, but FontCollection::hasVariationSelector
didn't acquire the lock. This caused a race condition.
This CL fixes this race condition.

Also, it turned out that assertMinikinLocked didn't assert even on
eng or userdebug device. This CL enables assertion on eng and userdebug
device since this assertion must be treated as bug.

BUG: 26323806

Change-Id: I9c4b1e1f09c6793e387fbdb8bb654cc0a13c65d5