Add Keystore get option that supresses caught exceptions warnings.

This is useful when the caught exceptions are not informative and they
act as a red herring in the adb logs.

Bug:109791294
Test: call this method in the VpnSettings and manually navigate to
adding a new VPN by searching for VPN in settings and then pressing '+'.

Change-Id: I4bc86e3ea5b11027090fd3a27dc7455557cf66ab