Remove RA solicit delay

It turns out that this breaks ipv6 config with NM. Instead what we want
is for glean to not up interfaces on boot (see the depends-on).

Change-Id: I6c5bc76c433e29f02d3266ab8f669015125ec954
Depends-On: https://review.opendev.org/#/c/688031

diskimage_builder/elements/simple-init/post-install.d/80-simple-init

@@ -45,17 +45,3 @@ case "$DIB_INIT_SYSTEM" in
         exit 1
         ;;
 esac
-
-if [[ ${DIB_SIMPLE_INIT_NETWORKMANAGER} != 0 ]]; then
-    # If we are using NetworkManager then we have to avoid having the kernel
-    # configure ipv6 addresses on an interface (via router advertisements)
-    # until NetworkManager starts. If the interface is configured by the
-    # kernel before NetworkManager then NetworkManager will ignore the
-    # interface and not configure ipv4 on it. It does this because it assumes
-    # some other entity is in control of the interface.
-    # Debian has a many year old long bug report detailing this behavior with
-    # the most interesting comment being at the end:
-    # https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=755202#331
-    DIB_SIMPLE_INIT_NETWORKMANAGER_IPV6_DELAY=${DIB_SIMPLE_INIT_NETWORKMANAGER_IPV6_DELAY:-30}
-    echo "net.ipv6.conf.default.router_solicitation_delay=${DIB_SIMPLE_INIT_NETWORKMANAGER_IPV6_DELAY}" >> /etc/sysctl.conf
-fi

releasenotes/notes/remove-solicit-delay-57a035b91922522a.yaml

@@ -0,0 +1,8 @@
+---
+deprecations:
+  - |
+    The ``DIB_SIMPLE_INIT_NETWORKMANAGER_IPV6_DELAY`` variable is removed as
+    it turned out that increasing this delay increased the odds that
+    NetworkManager would fail to configure IPv6 on an interface. Instead,
+    glean has been updated to not up interfaces and relies on NetworkManager
+    to do this. This results in reliable IPv4 and IPv6 config.