snp test is broken

[kraxel]

the snp test depends on the pxe test having configured the network beforehand, it does not work on its own.
swap the order of the tests ...

 pub fn test() {
     info!("Testing Network protocols");
 
-    pxe::test();
     snp::test();
+    pxe::test();
 }

... and watch it fail:

[PANIC]: panicked at uefi-test-runner/src/proto/network/snp.rs:112:9:
assertion `left == right` failed
  left: [0, 0, 0, 0, 0]
 right: [4, 4, 3, 2, 1]
Error: tests did not complete successfully

[phip1611]

Oh, good catch! It shouldn't be like that; test runs should be idempotent