MINOR: tcp-act: define optional arg name for attach-srv

MINOR: tcp-act: define optional arg name for attach-srv

Add an optional argument 'name' for attach-srv rule. This contains an
expression which will be used as an identifier inside the server idle
pool after reversal. To match this connection for a future transfer
through the server, the SNI server parameter must match this name. If no
name is defined, match will only occur with an empty SNI value.

For the moment, only the parsing step is implemented. An extra check is
added to ensure that the reverse server uses SSL with a SNI. Indeed, if
name is defined but server does not uses a SNI, connections will never
be selected on reused after reversal due to a hash mismatch.