EnvironmentTest.java: update testHidePid2 to support latest kernel

with the kernel change "proc: use human-readable values for hidepid"[1],
hidepid option for proc filesystem is printed as following:
    $ grep proc /proc/mounts
    proc /proc proc rw,relatime,gid=3009,hidepid=invisible 0 0
    $

and this change is to support for both hidepid=invisible and hidepid=2 formats

[1]: https://android.googlesource.com/kernel/common/+/1c6c4d112e81a919d4ea83ec6cbc2f55203217fd%5E%21/

Test: cts-tradefed run commandAndExit -m CtsOsTestCases -t android.os.cts.EnvironmentTest#testHidePid2
      with android-mainline and android12-5.4 kernel on hikey960 board

Signed-off-by: Yongqin Liu <yongqin.liu@linaro.org>
Change-Id: Iab79cd20ef51dfde729ddffe2ea6a1bd5a66139c
1 file changed