open GATT client didn't reserve the BLE link if open after connected.

need to reserve the BLE link to avoid BLE disconnection.
BTA_GATTC_OPEN_ERROR won't resereve the BLE link usage.
use BTA_GATTC_OPEN instead of BTA_GATTC_OPEN_ERROR to reserve the
BLE link. other the stack disconnect the BLE link due to no Gatt interface
use this connection.

bug:13228455
Change-Id: I1f9daa2171668f2ae535d998b401f1f0825d0451