Freeze {ipmemorystore,networkstack}-aidl-interfaces as version 2.

Generated with:
m networkstack-aidl-interfaces-freeze-api \
    ipmemorystore-aidl-interfaces-freeze-api

Test: builds, boots
Bug: 128803828
Change-Id: I079018679766738a97b827bc87a6903655f308dd
Merged-In: I079018679766738a97b827bc87a6903655f308dd
(cherry picked from commit 4570f866)