GATT server "Insufficient Encryption Key Size" tests are invalid

[sjanc]

Tests that verify GATT server "Insufficient Encryption Key Size" error code have couple issues:

1. they verify wrong ATT status code : should be ATT_ERROR_INSUFFICIENT_ENCRYPTION_KEY_SIZE (0x0c) instead of ATT_ERROR_INSUFFICIENT_ENCRYPTION (0x0f)
2. tests should pair with proper (small) key size before accessing characteristics and verifying returned status code

1 is easy to fix, 2 I have no idea on how this should be done, there is pairing_bv_01_c() which seems to be unused and this is only indication of pairing in those tests (unless I miss something)

This is affecting following tests:
GATT/SR/GAR/BI-11-C [Insufficient Encryption Key Size error - Reading Using Characteristic UUID]
GATT/SR/GAR/BI-17-C [Insufficient Encryption Key Size error - Reading Long Characteristic Value]
GATT/SR/GAR/BI-22-C [Insufficient Encryption Key Size error - Reading Multiple Characteristic Values]
GATT/SR/GAW/BI-06-C [Insufficient Encryption Key Size error - Writing Characteristic Value]
GATT/SR/GAW/BI-13-C [Insufficient Encryption Key Size error - Writing Long Characteristic Value]