Corrected buildtree_runner/README.md by putting 'sudo' in front of ./create_instance.sh

continuousintegration/buildtree_runner/README.md

@@ -75,7 +75,7 @@ The test instance can then be created by running (typically):
 
 ```
 cd ~/CTA/continuousintegration/orchestration
-./create_instance.sh -n ctatest -b /home/eric -B CTA-build -D -O
+sudo ./create_instance.sh -n ctatest -b /home/eric -B CTA-build -D -O
 ```
 
 and the tests will run like in the continuous integration environment.