CLEANUP: cli: simplify the "show cli sockets" I/O handler

CLEANUP: cli: simplify the "show cli sockets" I/O handler

The code is was a bit convoluted by the use of a state machine around
st2 that is not used since only the STAT_ST_LIST state was used, and
the test of global.cli_fe inside the loop while it ought better be
tested before entering there. Let's get rid of this unneded state and
simplify the code. There's no more need for ->st2 now. The code looks
more changed than it really is due to the reindent caused by the
removal of the switch statement, but "git show -b" shows what really
changed.