perf test shell: Replace '|&' with '2>&1 |' to work with more shells

perf test shell: Replace '|&' with '2>&1 |' to work with more shells

Since we do not specify bash (and/or zsh) as a requirement, use the
standard error redirection that is more widely supported.

BEFORE:

 $ sudo perf test -v 62
 62: Check open filename arg using perf trace + vfs_getname:
 --- start ---
 test child forked, pid 27305
 ./tests/shell/trace+probe_vfs_getname.sh: 20: ./tests/shell/trace+probe_vfs_getname.sh: Syntax error: "&" unexpected
 test child finished with -2
 ---- end ----
 Check open filename arg using perf trace + vfs_getname: Skip

AFTER:

 $ sudo perf test -v 62
 64: Check open filename arg using perf trace + vfs_getname               :
 --- start ---
 test child forked, pid 23008
 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

      0.361 ( 0.008 ms): touch/23032 openat(dfd: CWD, filename: /tmp/temporary_file.VEh0n, flags: CREAT|NOCTTY|NONBLOCK|WRONLY, mode: IRUGO|IWUGO) = 4
 test child finished with 0
 ---- end ----
 Check open filename arg using perf trace + vfs_getname: Ok

Similar to commit 35435cd06081, with the same title.

Signed-off-by: Kim Phillips <kim.phillips@arm.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Michael Petlan <mpetlan@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sandipan Das <sandipan@linux.vnet.ibm.com>
Cc: Thomas Richter <tmricht@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/20180629124633.0a9f4bea54b8d2c28f265de2@arm.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>