RFR [9] 8158525: Update a few java/net tests to use the loopback address instead of the host address

[Chris Hegarty]

The following networking tests have been seen to fail from a timeout, when the host 
is not accessible. These tests have nothing whatsoever to do with testing of network 
connections, they simply want to test the HTTP client implementation. This issue 
proposes to change the tests from using the host's name/address to using the 
loopback, to make them more robust. 

test/java/net/CookieHandler/CookieManagerTest.java 
test/java/net/HttpURLConnection/UnmodifiableMaps.java 
test/java/net/URLConnection/HandleContentTypeWithAttrs.java

http://cr.openjdk.java.net/~chegar/8158525/
https://bugs.openjdk.java.net/browse/JDK-8158525

-Chris.