test_095_kernel_symbols_missing_proc_self_stack failed with Xenial kernel

This is a split from bug 1800976, to make it become more specific to a single failure.

This test will fail with the proposed Xenial kernel.

  FAIL: test_095_kernel_symbols_missing_proc_self_stack (__main__.KernelSecurityTest)
  kernel addresses in /proc/self/stack are zeroed out
  ----------------------------------------------------------------------
  Traceback (most recent call last):
    File "./test-kernel-security.py", line 1341, in test_095_kernel_symbols_missing_proc_self_stack
      self._check_pK_files(self._095_kernel_symbols_missing_proc_self_stack, expected=expected)
    File "./test-kernel-security.py", line 1199, in _check_pK_files
      test_function(expected_restricted)
    File "./test-kernel-security.py", line 1297, in _095_kernel_symbols_missing_proc_self_stack
      expected, retry=True)
    File "./test-kernel-security.py", line 1136, in _read_twice
      self.assertEqual(rc, 0, regular)
  AssertionError: cat: /proc/self/stack: Permission denied

From Khaled's comment #1 in that bug:

    The commit "c714676a1 proc: restrict kernel stack dumps to root" (part of the update to linux-stable 4.4.160) has changed the permissions of /proc/self/stack to be root- and CAP_SYS_ADMIN-only which is causing test_095_kernel_symbols_missing_proc_self_stack to fail

So we might need to fix this from the test case perspective.

ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: linux-image-4.4.0-139-generic 4.4.0-139.165~14.04.1
ProcVersionSignature: User Name 4.4.0-139.165~14.04.1-generic 4.4.160
Uname: Linux 4.4.0-139-generic x86_64
ApportVersion: 2.14.1-0ubuntu3.29
Architecture: amd64
Date: Wed Nov 7 08:13:40 2018
SourcePackage: linux-lts-xenial
UpgradeStatus: No upgrade log present (probably fresh install)