Fix read_pid to support -n, --name option.

Fix a issue where read_pid was failing when a trema name was specified with -n or --name option.

Current read_pid checks the validity of the pid value obtaind from the .pid file 
by checking /proc/[pid]/exe matches the argument specified trema name.
This can be a problem when a trema application was started with a --name option.
where executable name does not always match trema names.

This patch will check /proc/[pid]/cmdline and check if -n or --name option was used, 
when /proc/../exe check failed.