Mark NetworkStack as updatable.

This is an updatable module. The flag enforces conformance to associated requirements with a module being updatable e.g. compiling against stable SDKs.

Bug: 153333044
Test: m
Change-Id: If34230b65fea3d73da28db2d6ee8a499b108f3ae
Merged-In: If34230b65fea3d73da28db2d6ee8a499b108f3ae
Exempt-From-Owner-Approval: clean cherry-pick
(cherry picked from commit 862a1a1f)