add cloud-init-run-module and ec2init/execute.py

cloud-init-run-module handles some boilerplate code for running
items on a 'frequency'.  It has the following usefulness

- a config module can be put into ec2init dir and implement a 'run'
  method that takes a list of arguments and the path to a config file
- it handles invoking module.run() only at a given frequency
  This is similar to karmic's ec2init's "run_once_ever" or run_once_per_ami

execute.py is an example module that executes the arguments given to it

An example usage in an upstart job would be with a 'exec' line like:

   exec cloud-init-run-module once_per_ami clean-core execute rm /var/run/core

The above would then run the command 'rm /var/run/core' only once

1 files changed, 14 insertions, 0 deletions

diff --git a/ec2init/execute.py b/ec2init/execute.py
new file mode 100644
index 00000000..d7386663
--- /dev/null
+++ b/ec2init/execute.py
@@ -0,0 +1,14 @@
+def run(list,cfg):
+    import subprocess
+    subprocess.Popen(list).communicate()
+    retcode = subprocess.call(list)
+
+    if retcode == 0:
+        return
+
+    if retcode < 0:
+        str="Cmd terminated by signal %s\n" % -retcode
+    else:
+        str="Cmd returned %s\n" % retcode
+    str+=' '.join(list)
+    raise Exception(str)