Use git client plugin 3.0.0-beta7

Includes automated test fixes for CentOS 6.

Author: MarkEWaite

pom.xml

@@ -83,7 +83,7 @@
     <dependency>
       <groupId>org.jenkins-ci.plugins</groupId>
       <artifactId>git-client</artifactId>
-      <version>3.0.0-rc</version>
+      <version>3.0.0-beta7</version>
     </dependency>
     <dependency>
       <groupId>org.jenkins-ci.plugins</groupId>