Skip a test when aggressive_connection_threshold is zero

Bug: 308483803
Bug: 378595485
Flag: com.android.bluetooth.flags.initial_conn_params_p1
Test: atest GattClientTest (after running below shell cmd)
      adb shell setprop \
      bluetooth.core.le.aggressive_connection_threshold 0
      (Checked that the test is skipped in this case.)
Change-Id: I775504514930311a89339d55a6a90483baa4ad8e