L2CAP: Add test case for TSPC_L2CAP_2_7 Can Sent Reject

Add following cert test in simple_l2cap_test:
  test_send_rej [L2CAP/ERM/BV-16-C]

Add following test case in pts_l2cap_test:
  test_L2CAP_ERM_BV_16_C

Bug: 149658425
Test: run_cert.sh
Change-Id: I4f160883d47d2294f88d98177813ec587a8c2e76