make sure that if builder configured with a non-standard (!= 3306)
default TCP port that value actually gets used throughout.


win/configure.js:
  Bug #15327: configure: --with-tcp-port option being partially ignored
      
  If MYSQL_TCP_PORT defaulted in configure (factory default 3306
  at the time of this writing), set MYSQL_TCP_PORT to factory
  default, then clear factory default after. That way, we lose no
  information, and we can distinguish between "defaulted" and the
  pathological case "builder specifically configured a port that
  coincides with factory default." This can in theory happen if
  builder configures and builds several servers from a script
  (--with-tcp-port=3306, --with-tcp-port=3316, --with-tcp-port=3326).
  Not all that probable, but much preferable to having more "magic"
  happen in the server when we can solve this without any guesswork.