Add support for ssh keys in cloud-config. move write_file to util.

----
#cloud-config
apt_update: true
ssh_keys:
  rsa_private: |
    -----BEGIN RSA PRIVATE KEY-----
    MIIBxwIBAAJhAKD0YSHy73nUgysO13XsJmd4fHiFyQ+00R7VVu2iV9Qcon2LZS/x
    ...
    REPPOyrAspdeOAV+6VKRavstea7+2DZmSUgE
    -----END RSA PRIVATE KEY-----

  rsa_public: ssh-rsa AAAAB3NzaC1yc2E...18QJvWPocKJtlsDNi3 smoser@host

  dsa_private: |
    -----BEGIN DSA PRIVATE KEY-----
    MIIBuwIBAAKBgQDP2HLu7pTExL89USyM0264RCyWX/CMLmukxX0Jdbm29ax8FBJT
    ...
    8KucvUYbOEI+yv+5LW9u3z/BAoGBAI0q6JP+JvJmwZFaeCMMVxXUbqiSko/P1lsa
    -----END DSA PRIVATE KEY-----

  dsa_public: ssh-dss AAAAB3NzaC1kc3M...ybngIy66PMEoQ= smoser@host
----

1 files changed, 15 insertions, 0 deletions

diff --git a/ec2init/util.py b/ec2init/util.py
index c1da0e71..0737f117 100644
--- a/ec2init/util.py
+++ b/ec2init/util.py
@@ -1,4 +1,6 @@
 import yaml
+import os
+import errno
 
 def read_conf(fname):
 	stream = file(fname)
@@ -27,3 +29,16 @@ def mergedict(src,cand):
             else:
                 src[k] = mergedict(src[k],v)
     return src
+
+def write_file(file,content,mode=0644):
+        try:
+            os.makedirs(os.path.dirname(file))
+        except OSError as e:
+            if e.errno != errno.EEXIST:
+                raise e
+
+        f=open(file,"wb")
+        f.write(content)
+        f.close()
+        os.chmod(file,mode)
+