Add already calibrated check in grip_cuff_ex init
Add already calibrated check in grip_cuff_ex init

Checks if gripper is already calibrated before attempting
calibration on non-custom grippers, so that every gripper isn't
re-calibrated when example is started.

jaspell/baxter_examples,RethinkRobotics/baxter_examples,Sannoso/baxter_examples,wjchen84/baxter_examples