cli: cloud-id report not-run or disabled state as cloud-id (#1162)

This fix has two elements:
 - cloud-init status will not correctly report 'not-run' prior to systemd
   generator running. Only report "disabled" when generator has run
   and /run/cloud-init/disabled exists.
 -  Expose not-run and disabled state in cloud-id responses
 -  Add unique error codes from cloud-id for error, disabled and not-run.
  
The new cloud-id exit codes:
 0: success
 1: error
 2: cloud-init is in disabled state
 3: cloud-init generator has not run yet

1 files changed, 23 insertions, 0 deletions

diff --git a/doc/man/cloud-id.1 b/doc/man/cloud-id.1
index 59fecdd9..c56587c8 100644
--- a/doc/man/cloud-id.1
+++ b/doc/man/cloud-id.1
@@ -6,6 +6,15 @@ cloud-id \- Report the canonical cloud-id for this instance
 .SH SYNOPSIS
 .BR "cloud-id" " [-h] [-j] [-l] [-i <INSTANCE_DATA>]"
 
+.SH DESCRIPTION
+cloud-id is the lowercase name of the cloud datasource discovered.
+
+The cloud-id will be 'not-run' when systemd generator has not run yet.
+The cloud-id will be 'disabled' when cloud-init is disabled or when
+ds-identify did not find a valid datasource.
+
+See cloud-init status --long for more information.
+
 .SH OPTIONS
 .TP
 .B "-h, --help"
@@ -24,6 +33,20 @@ Report extended cloud-id information as tab-delimited string
 Path to instance-data.json file. Default is
 /run/cloud-init/instance-data.json
 
+.SH EXIT STATUS
+.TP
+0
+On success
+.TP
+1
+Due to an error
+.TP
+2
+Due to cloud-init in a disabled state. See: cloud-init status --long
+.TP
+3
+The cloud-init generator and discovery has not yet run.
+
 .SH COPYRIGHT
 Copyright (C) 2021 Canonical Ltd. License GPL-3 or Apache-2.0