Fix potential race introduced in Icd7f5f03

Digit wrote:

"You probably don't want to close the socket here without updating
c->socket as well. Otherwise, another thread holding a handle to the
client after the c->decRef() could end up sending a message to a
different socket, if the file descriptor index is reused by another
client in the meantime."

Change-Id: Icdefb5ffc0c7607325d7db761e1f04e5d868bfb7