Fix checkCalledFromInit

This function checks if it is called from init() by looking into
callers. By the way, it may fail when init() is inlined.

To fix this, CallersFrames() is used to translate PCs into symbolic
information accounting for inlined functions.

Test: go test ./...
Change-Id: I18b3c3ffdaf71f775e3522c87607aec5df7b09c5