More ProblemList.txt updates (5/2013)

This issue proposes to add four networking related tests to the ProblemList until the issues can be resolved.

+#8014720
+java/net/ResponseCache/B6181108.java generic-all
+
+#8014723
+sun/misc/URLClassPath/ClassnameCharTest.java generic-all
+
+#8014719
+sun/net/www/http/HttpClient/ProxyTest.java generic-all