CLOUDSTACK-8011: Upgrade maven dependencies

Changes;
- Upgrades maven-war plugin to 4.5 (faster war packaging)
- Upgrade spring framework to latest minor release
- Upgrade ehcache, jasypt, httpclient, httpcore and other core dependencies
- Upgrade mockito, powermock dependencies
- Upgrade to latest ipv6 library, fix unit test NetUtilsTest

Newer dependencies can be listed using:
mvn versions:display-dependency-updates -Dnoredist -Dsimulator -P developer,systemvm

Testing;
- Tested using Maven 3.2.1
- Local noredist build with unit tests succeeds
- CloudStack mgmt server started, basic business layer tests work
- Observed 10-15% build time improvement using new maven-war plugin

Signed-off-by: Rohit Yadav <rohit.yadav@shapeblue.com>