Revert "[maven-release-plugin] prepare for next development iteration"

This reverts commit 9e9eacc4d33e03d557d4c5d57b9bdafb6e27e245.
Revert "[maven-release-plugin] prepare release helix-0.7.1"

This reverts commit ea0300083560ffb45cb8070cb2dcdb2f5ddc93ed.
[maven-release-plugin] prepare release helix-0.7.1
[maven-release-plugin] prepare for next development iteration