Reject Session Modifications with multiple rule changes with same ID

[ivan4th]

3GPP TS 29.244 6.3.3.2 CP Function behaviour:

The CP function shall not include multiple updates in a PFCP Modification Request message, e.g. Create PDR, Update PDR and Remove PDR, for the same rule identified by the Rule ID.

This also concerns URRs, QERs, etc. Presently, UPG doesn't detect such situations and they may result in unpredictable behavior. Moreover, PDR replacement test in E2E is implemented incorrectly as it deletes and re-creates PDRs in the same Session Modification Request.