Fix netlink group mismatch in fds used for offload

Existing groups used for binding to netlink conntrack events don't
seem to work as expected. Fix this by using exact groups defined
in IOffloadConfig hal.

Test: as follows
      - Compiles and boots on walleye
      - Validated conntrack destroy events are received as expected.
      - Validated offload works as expected.

Bug:68018148
CRs-fixed:2126789

Merged-In: I2dcebec1c08bb7b067621331533d8a65dd7b5083
Merged-In: I96d6d5601aff009879f452975be91b6e7e40bb57
Change-Id: I76178fd7f109b82a4e4961347b8949937813d71d
(cherry picked from commit f10282b830af4c7ea56b2c64e73a7ffd3c006007)

• services/core/jni/com_android_server_connectivity_tethering_OffloadHardwareInterface.cpp[diff]