NEXUS-5963: Do not export nonProxyHosts to system props

As those are in Nexus specific format (regex) and does not
follow the JDK standard for this system property.
NEXUS-5963: Adjust UT
Merge pull request #188 from sonatype/NEXUS-5963-non-proxy-hosts

NEXUS-5963: Do not export nonProxyHosts to system props