Enable ec2_utils to stop retrying to get ec2 metadata

Signed-off-by: David Sloboda <david.x.sloboda@oracle.com>
Reviewed-by: Laurence Rochfort <laurence.rochfort@oracle.com>

diff -ruN a/cloudinit/sources/helpers/openstack.py b/cloudinit/sources/helpers/openstack.py
--- a/cloudinit/sources/helpers/openstack.py	2018-04-02 12:51:20.053828637 -0700
+++ b/cloudinit/sources/helpers/openstack.py	2018-04-02 12:33:20.000000000 -0700
@@ -464,6 +464,16 @@
 
         return results
 
+def should_retry_cb(_request_args, cause):
+    try:
+        code = int(cause.code)
+        if code >= 400:
+            return False
+    except (TypeError, ValueError):
+        # Older versions of requests didn't have a code.
+        pass
+    return True
+
 
 class MetadataReader(BaseReader):
     def __init__(self, base_url, ssl_details=None, timeout=5, retries=5):
@@ -489,16 +499,6 @@
         return self._versions
 
     def _path_read(self, path, decode=False):
-        def should_retry_cb(_request_args, cause):
-            try:
-                code = int(cause.code)
-                if code >= 400:
-                    return False
-            except (TypeError, ValueError):
-                # Older versions of requests didn't have a code.
-                pass
-            return True
-
         response = url_helper.readurl(
             path,
             retries=self.retries,
@@ -519,6 +519,7 @@
             ssl_details=self.ssl_details,
             timeout=self.timeout,
             retries=self.retries,
+            exception_cb=should_retry_cb,
         )