dumpsys: display the client PIDs of all of the services

When gathering info on a service, get the BpBinder handle to look up the
node number of the binder service in binder_logs/proc/<pid>.
Look up the node number in binder_logs/state from the binder service.
That entry in the state file has the client PIDs.

Example output:
$ adb shell dumpsys --clients android.hardware.power.IPower/default
Client PIDs: 437, 708, 203

Test: adb root && adb shell dumpsys --clients
Test: adb shell dumpsys --clients power
Test: adb shell dumpsys --clients --pid
Change-Id: I0daebc18cb9f47925ccec5a3eb0b09c4b1e43fe4