DO NOT MERGE BLE HID device connection failure due to security error.

When HID BLE device start encryption, if some other GATT application
already start encryption(but not finished yet) by calling
gatt_security_check_start. The HID BLE device will be failed to start
encryption, which will cause it to disconnect the BLE HID connection.
The solution is to check whether we already started the encryption
, If the encryption is already started, wait until the encryption
finished, then continue to start security check for BLE HID device.
add encrytion complete event to notify all GATT client encryption done.
filter the event just for BTA HH LE GATT client.

bug:11636246
Change-Id: If58e57c623cc8cfa05208587b010bec68c71306c