print log message for values retrieved from configstore

This CL adds a code for printing log messages in clients-side utility
library functions (getXXX) for configstore so that the developer can
figure out which configuration values are actually retrieved from the configstore.

Bug: 36275627
Test: Built and check the log message appears

Change-Id: I2c0895f8afbbb2947b62164acaf62a491c451dc0