perf test shell: Add test using probe:vfs_getname and verifying results

perf test shell: Add test using probe:vfs_getname and verifying results

This test uses the 'perf test shell' library to add probe:vfs_getname to the
system then use it with 'perf record' using 'touch' to write to a temp file,
then checks that that was captured by the vfs_getname probe in the generated
perf.data file, with the temp file name as the pathname argument.

Using it:

  # perf test "Use vfs_getname"
  60: Use vfs_getname probe to get syscall args filenames: Ok
  # perf test -v "Use vfs_getname"
  60: Use vfs_getname probe to get syscall args filenames:
  --- start ---
  test child forked, pid 16414
  Added new event:
    probe:vfs_getname    (on getname_flags:72 with pathname=result->name:string)

  You can now use it in all perf tools, such as:

	perf record -e probe:vfs_getname -aR sleep 1

  Recording open file:
  [ perf record: Woken up 1 times to write data ]
  [ perf record: Captured and wrote 0.022 MB /tmp/vaca.perf.data.QZsn7 (13 samples) ]
  Looking at perf.data file for vfs_getname records for the file we touched:
             touch 16421 [002] 1255152.879561: probe:vfs_getname: (ffffffffa626e608) pathname="/tmp/vaca.l10SL"
  test child finished with 0
  ---- end ----
  Use vfs_getname probe to get syscall args filenames: Ok
  #

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Michael Petlan <mpetlan@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Thomas Richter <tmricht@linux.vnet.ibm.com>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/n/tip-t555fnhbcbxnukltk23dqxur@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>