Detect DRILL_VERSION from git.properties (#528)

This would address issues arising out of 4 digit versioning of Drill or any other similar changes (e.g. version...-SNAPSHOT)
diff --git a/conf/drillTestConfig.properties.example b/conf/drillTestConfig.properties.example
index 6b841c2..376405a 100644
--- a/conf/drillTestConfig.properties.example
+++ b/conf/drillTestConfig.properties.example
@@ -146,7 +146,7 @@
 export M2=$M2_HOME/bin
 export PATH=.:$M2:$PATH
 
-export DRILL_VERSION=1.6.0-SNAPSHOT
+export DRILL_VERSION=$(grep 'git.build.version' ${DRILL_HOME}/git.properties | tr '=' '\n' | tail -1)
 export HADOOP_VERSION=1.0.3-mapr-3.0.2
 export USERNAME
 export PASSWORD