Handle kernel boot options

The 'system.kernel.elevator' and 'system.kernel.isolcpu' options
have been kept for backward compatibility and should be used in new
fashion way with system.kernel.boot_options parameter.

Change-Id: I51f7167b8b8946500df2065ee6b02bcf21809bc9
diff --git a/tests/pillar/system.sls b/tests/pillar/system.sls
index d542587..bcbfa08 100644
--- a/tests/pillar/system.sls
+++ b/tests/pillar/system.sls
@@ -19,6 +19,9 @@
     kernel:
       isolcpu: 1,2,3,4
       elevator: deadline
+      boot_options:
+        - pti=off
+        - spectre_v2=auto
     cgroup:
       group:
         group_1: