dispatcher: add MS Azure endpoint env var expected by cloud-init

Some linux distros (e.g., RHEL, CentOS and Fedora) ship a dispatcher
script with their dhclient package in order to run user dhclient hook
scripts also when connections are run by NetworkManager.
The scripts convert the var names in the environment to the ones
expected in the dhclient hook scripts.
This feature is currently use by cloud-init to retrieve the MS Azure
server endpoint address, which is sent in the private dhcp option 245.
We just redefined the default dhclient var names for the private options
from "unknown_xyz" to "private_xyz". In order to let current cloud-init
version to be able to retrieve the Azure server endpoint address, add
the legacy var name "unknown_245" to the dispatcher script environment.
14 jobs for fg/dhcp_options2env-rh1663253 in 50 minutes and 39 seconds (queued for 8 seconds)
latest
Status Job ID Name Coverage
  Test
passed #402268
allowed to fail
checkpatch

00:01:14

manual #402273
allowed to fail manual
t_centos:7.5.1804
passed #402274
t_centos:7.6.1810

00:25:47

passed #402277
t_debian:9

00:16:54

passed #402279
t_debian:sid

00:17:34

manual #402278
allowed to fail manual
t_debian:testing
passed #402269
t_fedora:28

00:35:40

passed #402270
t_fedora:29

00:38:30

failed #402271
t_fedora:30

00:17:57

manual #402272
allowed to fail manual
t_fedora:rawhide
passed #402275
t_ubuntu:16.04

00:29:54

passed #402276
t_ubuntu:18.04

00:29:36

 
  External
passed NetworkManager test verification

passed NetworkManager test verification

05:30:32

 
Name Stage Failure
failed
t_fedora:30 Test
(./src/platform/tests/test-link-linux:1638): NetworkManager-DEBUG: 13:36:06.216: <debug> [1562333766.2169] platform: (t-00089) link: deleting
# NetworkManager-DEBUG: <trace> [1562333766.3224] platform-linux: delayed-action: schedule wait-for-nl-response (seq 3496, timeout in 0.199988655, response-type 0)
(./src/platform/tests/test-link-linux:1638): NetworkManager-DEBUG: 13:36:06.322: <trace> [1562333766.3224] platform-linux: delayed-action: schedule wait-for-nl-response (seq 3496, timeout in 0.199988655, response-type 0)
# NetworkManager-DEBUG: <trace> [1562333766.3224] platform-linux: delayed-action: handle wait-for-nl-response (any)
(./src/platform/tests/test-link-linux:1638): NetworkManager-DEBUG: 13:36:06.322: <trace> [1562333766.3224] platform-linux: delayed-action: handle wait-for-nl-response (any)
# NetworkManager-DEBUG: <trace> [1562333766.3225] platform-linux: netlink: recvmsg: new message RTM_DELLINK, flags 0, seq 0
(./src/platform/tests/test-link-linux:1638): NetworkManager-DEBUG: 13:36:06.322: <trace> [1562333766.3225] platform-linux: netlink: recvmsg: new message RTM_DELLINK, flags 0, seq 0
# NetworkManager-DEBUG: <trace> [1562333766.3225] platform-linux: event-notification: RTM_DELLINK, flags 0, seq 0: 223
(./src/platform/tests/test-link-
Job's log exceeded limit of 16777216 bytes.