BUG/MEDIUM: cli: Handle applet shutdown when waiting for a command line

BUG/MEDIUM: cli: Handle applet shutdown when waiting for a command line

When the CLI applet was refactord in the commit 20ec1de21 ("MAJOR: cli:
Refacor parsing and execution of pipelined commands"), a regression was
introduced. The applet shutdown was not longer handled when the applet was
waiting for the next command line. It is especially visible when a client
timeout occurred because the client connexion is no longer closed.

To fix the issue, the test on the SE_FL_SHW flag was reintroduced in
CLI_ST_PARSE_CMDLINE state, but only is there is no pending input data.

It is a 3.2-specific issue. No backport needed.