Set SA mark to unused for Tunnel Mode

This change updates the kernel network tests to reflect how the platform
will be using IPsec. Specifically, limitations regarding how SAs are
created require SPIs be allocated first, and the kernel does not
currently support updating marks on larval SAs.

Bug: 78126996
Test: Ran on 3.18, 4.4, 4.9 and net-next kernels
Change-Id: Iba12f10621630b2d1d9dc75187327d6388dd4ffa