Camera: HDR: don't reset focus manager when HDR is active.

HDR takes time to compute. So disable any refernce to zsl except
for actual take it in zsl command.
due to a recent commit http://review.cyanogenmod.org/#/c/45730/
I didn't know it was merged in less than 24 hours as HDR commit.

Change-Id: I2aa3f4146575329c6fefb259b099371080842dab