azure dhclient-hook cleanups

This adds some function to the generator to maintain the presense of a
flag file '/run/cloud-init/enabled' indicating that cloud-init is enabled.

Then, only run the dhclient hooks if on Azure and cloud-init is enabled.
The test for is_azure currently only checks to see that the board vendor
is Microsoft, not actually that we are on azure.  Running should not be
harmful anywhere, other than slowing down dhclient.

The value of this additional code is that then dhclient having run
does not task the system with the load of cloud-init.

Additionally, some changes to config are done here.
 * rename 'dhclient_leases' to 'dhclient_lease_file'
 * move that to the datasource config (datasource/Azure/dhclient_lease_file)

Also, it removes the config in config/cloud.cfg that set agent_command
to __builtin__.  This means that by default cloud-init still needs
the agent installed.  The suggested follow-on improvement is to
use __builtin__ if there is no walinux-agent installed.

1 files changed, 3 insertions, 6 deletions

diff --git a/doc/sources/azure/README.rst b/doc/sources/azure/README.rst
index 48f3cc7a..ec7d9e84 100644
--- a/doc/sources/azure/README.rst
+++ b/doc/sources/azure/README.rst
@@ -30,13 +30,10 @@ datasource:
 If those files are not available, the fallback is to check the leases file
 for the endpoint server (again option 245).
 
-You can define the path to the lease file with the 'dhclient_lease' configuration
-value under system_info: and paths:.  For example:
+You can define the path to the lease file with the 'dhclient_lease_file'
+configuration.  The default value is /var/lib/dhcp/dhclient.eth0.leases.
 
-      dhclient_lease: /var/lib/dhcp/dhclient.eth0.leases
-
-If no configuration value is provided, the dhclient_lease value will fallback to
-/var/lib/dhcp/dhclient.eth0.leases.
+    dhclient_lease_file: /var/lib/dhcp/dhclient.eth0.leases
 
 walinuxagent
 ------------