关于DUN中TC_GW_TER_XXX fail的 cases

[DESCRIPTION]
BQB认证时经常碰到DUN这样的fail case：
Test case : TC_GW_TER_BV_01_I started
- ProtocolDescriptorList: DUN Gateway SPP channel retrieved successfully
- AT: SPP connect succeeded
- Connection setup successfully.
- ATZ command successfully responded.
- ATE0 command successfully responded.
- ATM0 command successfully responded.
- ATL0 command successfully responded.
- ATS7=60 command successfully responded.
- ATX4 command successfully responded.
- ATD*99# command send completed.
- DUN data received.
- Data send successfully responded.
- DT transmit connect setup successfully. No data or file been transfered.
- The response to the following AT command has timed out: +++
- AT: Service Level Connection disabled
Final Verdict : None
[SOLUTION]
此“+++”command为PTS的问题，目前DUN TER的cases 用PTS4.5及4.5以上版本无法跑pass，请改用PTS4.3或者4.4跑即可pass。
此DUN的PTS issue请参考：
https://www.bluetooth.org/pts/issues/view_issue.cfm?id=9557