Fixed command for installing python via apt-get and yum by using sudo

Cherry-picked Jongyoul Lee’s commit (a0341a4, PR #105), but conflicts 
due to server-cli/src/main/resources/catalog.bom not existing. Therefore
fixing conflict manually and committing.
diff --git a/server-cli/src/main/resources/brooklyn/default.catalog.bom b/server-cli/src/main/resources/brooklyn/default.catalog.bom
index deca965..c1f0456 100644
--- a/server-cli/src/main/resources/brooklyn/default.catalog.bom
+++ b/server-cli/src/main/resources/brooklyn/default.catalog.bom
@@ -97,8 +97,8 @@
           install.command: |
             # install python if not present
             which python || \
-              { apt-get update && apt-get install python ; } || \
-              { yum update && yum install python ; } || \
+              { sudo apt-get update && sudo apt-get install python ; } || \
+              { sudo yum update && sudo yum install python ; } || \
               { echo WARNING: cannot install python && exit 1 ; }
 
           customize.command: |