[NEXUS-7659] Disable all SSL (including SSLv3) protocols by default

https://issues.sonatype.org/browse/NEXUS-7659
http://bamboo.s/browse/NX-OSSF390

Similar to changes done in http client 4.3.6 SSLConnectionSocketFactory
The code snippet in http://www.oracle.com/technetwork/java/javase/documentation/cve-2014-3566-2342133.html uses `getEnabledProtocols` and strips out just the SSLv3 and SSLv2Hello protocols, whereas this takes the result from `getSupportedProtocols` and removes all SSL protocols. At first glance this doesn't appear to match what https://issues.sonatype.org/browse/NEXUS-7659 was proposing, so I'm curious why this uses a different approach.