ftests: Add cgget test with multiple '-r' flags and multiple cgroups

ftests: Add cgget test with multiple '-r' flags and multiple cgroups

Add a test that exercises multiple '-r' flags and multiple
cgroups in cgget.  This test verifies the following cgget
operation:

	$ cgget -r memory.limit_in_bytes -r memory.soft_limit_in_bytes \
	  012cgget1 012cgget2

-----------------------------------------------------------------
Test Results:
        Run Date:                          Feb 09 21:39:23
        Passed:                                  1 test(s)
        Skipped:                                 0 test(s)
        Failed:                                  0 test(s)
-----------------------------------------------------------------
Timing Results:
        Test                                    Time (sec)
        ---------------------------------------------------------
        setup                                        16.92
        012-cgget-multiple_r_flags2.py                1.83
        teardown                                      0.00
        ---------------------------------------------------------
        Total Run Time                               18.75

Signed-off-by: Tom Hromatka <tom.hromatka@oracle.com>