Enable algorithm net tests for 3.18 kernels

With the backport of 00bc0ef, 3.18 kernels no longer hang on the
xfrm algorithm tests. This patch re-enables these tests for all 3.18
kernels.

Bug: 63589559
Test: All kernel tests run, passing.
Merged-In: I27b7e463a5566b1211ef6248f9239a52ff39d50d
Change-Id: I27b7e463a5566b1211ef6248f9239a52ff39d50d
(cherry picked from commit 2ab89c98)