disable the DAP remote tests

Intermittent availability of the DAP endpoints tested means that sometimes a perfectly working build is failed. This has been documented [by others](http://www.unidata.ucar.edu/support/help/MailArchives/netcdf/msg12090.html), and distributions like PLD linux [also disable these tests](http://lists.pld-linux.org/mailman/pipermail/pld-cvs-commit/Week-of-Mon-20110627/314985.html) because of this issue.