perf test: Change to use bash for daemon test

When executing the daemon test on Arm64 and x86 with Debian (Buster)
distro, both skip the test case with the log:

  # ./perf test -v 76
  76: daemon operations                                               :
  --- start ---
  test child forked, pid 11687
  test daemon list
  trap: SIGINT: bad trap
  ./tests/shell/daemon.sh: 173: local: cpu-clock: bad variable name
  test child finished with -2
  ---- end ----
  daemon operations: Skip

So the error happens for the variable expansion when use local variable
in the shell script.  Since Debian Buster uses dash but not bash as
non-interactive shell, when execute the daemon testing, it hits a known
issue for dash which was reported [1].

To resolve this issue, one option is to add double quotes for all local
variables assignment, so need to change the code from:

  local line=`perf daemon --config ${config} -x: | head -2 | tail -1`

  ... to:

  local line="`perf daemon --config ${config} -x: | head -2 | tail -1`"

But the testing script has bunch of local variables, this leads to big
changes for whole script.

On the other hand, the testing script asks to use the "local" feature
which is bash-specific, so this patch explicitly uses "#!/bin/bash" to
ensure running the script with bash.

After:

  # ./perf test -v 76
  76: daemon operations                                               :
  --- start ---
  test child forked, pid 11329
  test daemon list
  test daemon reconfig
  test daemon stop
  test daemon signal
  signal 12 sent to session 'test [11596]'
  signal 12 sent to session 'test [11596]'
  test daemon ping
  test daemon lock
  test child finished with 0
  ---- end ----
  daemon operations: Ok

[1] https://bugs.launchpad.net/ubuntu/+source/dash/+bug/139097

Fixes: 2291bb91 ("perf tests: Add daemon 'list' command test")
Signed-off-by: Leo Yan <leo.yan@linaro.org>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lore.kernel.org/lkml/20210320104554.529213-1-leo.yan@linaro.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/tests/shell/daemon.sh

-#!/bin/sh
+#!/bin/bash
 # daemon operations
 # SPDX-License-Identifier: GPL-2.0