OPENDJ-2693 dsconfig error message is showing the wrong port

The ConnectionFactoryProvider is storing the port in two places: an IntegerArgument and an int field.
Remove the int field and only keep the IntegerArgument to be consistent with other arguments.

ConnectionFactoryProvider.java:
Removed port field.
In getPort(), conditionally read the port from standard input.
if running in interactive mode and the port argument was not provided before
In getConnectionFactory(), avoid repeting conditions.