lshal: Add option to print cmd lines instead of pids.

Add -m to arguments of lshal. When this flag is set,
/proc/{pid}/cmdline is printed instead of a plain PID.
If the file doesn't exist, it will be striped out from
the PID column as well (the process is considered died
and won't hold a reference to the binder object.)

Test: lshal -icm

Bug: 35160832

Change-Id: I4345bf06112a1f87ce91bec6f6f787703e46cd17