update process running test case for dhcpcd

Summary:
With D40090857 landed, ifupdown will start the dhcpcd with both IPv4 and IPv6.
Update the Process Running test case.

Test Plan:
Build test with QEMU
```
root@bmc-oob:~# python3 /tmp/tests2/cit_runner.py -s /tmp/tests2 --platform grandcanyon -r tests.grandcanyon.test_process_running
test_installed_processes (tests.grandcanyon.test_process_running.ProcessRunningTest) ... ok

----------------------------------------------------------------------
Ran 1 test in 0.220s

OK
```

Reviewed By: doranand

fbshipit-source-id: 522dd3567ab45c75932f47c09d95fef5a09cfbb2

Author: zhdaniel12

tests2/tests/grandcanyon/test_process_running.py

@@ -28,8 +28,7 @@ def set_processes(self):
             "fscd",
             "sshd",
             "rsyslogd",
-            "dhcpcd: eth0 [ip4]",
-            "dhcpcd: eth0 [ip6]",
+            "dhcpcd: eth0 [ip4] [ip6]",
             "mTerm_server",
             "sensord",
             "healthd",