BUG/MINOR: mworker/cli: 'show proc' is limited by buffer size

BUG/MINOR: mworker/cli: 'show proc' is limited by buffer size

In ticket #3204, it was reported that "show proc" is not able to display
more than 202 processes. Indeed the bufsize is 16k by default in the
master, and can't be changed anymore since 3.1.

This patch allows the 'show proc' to start again to dump when the buffer
is full, based on the timestamp of the last PID it attempted to dump.
Using pointers or count the number of processes might not be a good idea
since the list can change between calls.

Could be backported in all stable branche.