Add IPsec tunnel mode feature flag

This patch adds a feature flag for IPsec Tunnel Mode. This implies VTI
(with output-mark updating), or XFRM-I in the kernels.

Bug: 117183273
Test: Compiles
Change-Id: I6dd0e429cc0bd100f2ef1140a6651f6ef5294c79
Merged-In: I6dd0e429cc0bd100f2ef1140a6651f6ef5294c79
(cherry picked from commit dc92c69b087d5fbecff76ef1e739ae415312734d)
2 files changed