BUG/MINOR: cli: Ensure all command outputs end with a LF

BUG/MINOR: cli: Ensure all command outputs end with a LF

Since 200b0fac ("MEDIUM: Add support for updating TLS ticket keys via
socket"), 4147b2ef ("MEDIUM: ssl: basic OCSP stapling support."),
4df59e9 ("MINOR: cli: add socket commands and config to prepend
informational messages with severity") and 654694e1 ("MEDIUM: stats/cli:
add support for "set table key" to enter values"), commands
'set ssl tls-key', 'set ssl ocsp-response', 'set severity-output' and
'set table' do not always send an extra LF at the end of their outputs.

This is required as mentioned in doc/management.txt:

"Since multiple commands may be issued at once, haproxy uses the empty
line as a delimiter to mark an end of output for each command"

Signed-off-by: Aurélien Nephtali <aurelien.nephtali@corp.ovh.com>