apps/bttester: do not distribute CSRK
apps/bttester: do not distribute CSRK

BLE_SM_OUR_KEY_DIST and BLE_SM_THEIR_KEY_DIST should be set to 3,
as we do not support security mode 2 - CSRK shall not be distributed.

apache/mynewt-nimble,apache/mynewt-nimble,apache/mynewt-nimble,apache/mynewt-nimble,apache/mynewt-nimble