[request] Make sure set_message() actually displays its given message (closes #3003425) The default automatic form sets a standard submit message as session data. However in some cases, such as the cancellation of a form edition, another message is intended to be printed on-screen. This patch makes sure that set_message() really scrubs all previous messages (and ids) from the request object and from the session data.

[MESSAGES CONTROL]
disable-msg = C0301

[VARIABLES]
# Enable / disable this checker
enable-variables = yes
additional-builtins = _, display_name

[BASIC]
required-attributes=
attr-rgx = (w|[a-z_][a-z0-9_]{2,30})
variable-rgx = (w|[a-z_][a-z0-9_]{2,30})$
argument-rgx = (w|[a-z_][a-z0-9_]{2,30})$

[TYPECHECK]
generated-members=debug,info,notice,warning,error,critical,exception