Zero-initialize struct which contains kernel structs.

This one struct initialization results in two uninitialized
xfrm_address_t objects. Those objects are then filled in with correctly
initialized values. There is no bug here, but we should maintain struct
hygiene.

Bug: 65693875
Test: runtest -x system/netd/server/netd_unit_test.cpp
Change-Id: Ie61971f0965ce7054d5194ac8ca7991eee214a3e