brick-mux : fix spurious socket connect failure issue during volume stop

[atinmu]

Change the logic of using the parent socket file to send the detach request by picking it up from /proc//cmdline where pid is the process id of the parent brick. During Multiplex, this would avoid creating a hard link of a socket file.

Credits : [email protected] for helping with the utility function

Fixes: #1468 Signed-off-by: Atin Mukherjee [email protected]

[rishubhjain]

retest this please

[rishubhjain]

retest this please