Conditionally restore default route in setup_ipv6

Restoring the default IPv6 route is not needed in CI and
fails when there are multiple defaults, but it is useful
in local devstacks where multiple default routes are not
typical.

Add a variable in settings and use it to make this behavior
conditional and set it to False for the lvm job.

Closes-bug: #1836788
Change-Id: Id73de8100509ec5935641f5f35f93f482d108bcd
(cherry picked from commit 70e908344d)
(cherry picked from commit 99c0a11092)

contrib/ci/pre_test_hook.sh

@@ -186,6 +186,7 @@ if [[ "$MANILA_SETUP_IPV6" == True ]]; then
     # regular Neutron DevStack configuration.
     echo "NEUTRON_CREATE_INITIAL_NETWORKS=False" >> $localconf
     echo "IP_VERSION=4+6" >> $localconf
+    echo "MANILA_RESTORE_IPV6_DEFAULT_ROUTE=False" >> $localconf
 fi
 
 if [[ "$DRIVER" == "generic"* ]]; then

devstack/plugin.sh

@@ -953,8 +953,12 @@ function install_libraries {
 
 function setup_ipv6 {
 
-    # save IPv6 default route to add back later after enabling forwarding
-    local default_route=$(ip -6 route | grep default | cut -d ' ' -f1,2,3,4,5)
+    # This will fail with multiple default routes and is not needed in CI
+    # but may be useful when developing with devstack locally
+    if [ $(trueorfalse False MANILA_RESTORE_IPV6_DEFAULT_ROUTE) == True ]; then
+        # save IPv6 default route to add back later after enabling forwarding
+        local default_route=$(ip -6 route | grep default | cut -d ' ' -f1,2,3,4,5)
+    fi
 
     # make sure those system values are set
     sudo sysctl -w net.ipv6.conf.lo.disable_ipv6=0
@@ -1053,9 +1057,13 @@ function setup_ipv6 {
         sudo systemctl restart bgpd
     fi
 
-    # add default IPv6 route back
-    if ! [[ -z $default_route ]]; then
-        sudo ip -6 route add $default_route
+    # This will fail with mutltiple default routes and is not needed in CI
+    # but may be useful when developing with devstack locally
+    if [ $(trueorfalse False MANILA_RESTORE_IPV6_DEFAULT_ROUTE) == True ]; then
+        # add default IPv6 route back
+        if ! [[ -z $default_route ]]; then
+            sudo ip -6 route add $default_route
+        fi
     fi
 
 }

devstack/settings

@@ -197,6 +197,7 @@ MANILA_DATA_COPY_CHECK_HASH=${MANILA_DATA_COPY_CHECK_HASH:=True}
 
 # Manila IPv6 Setup flag
 MANILA_SETUP_IPV6=${MANILA_SETUP_IPV6:=False}
+MANILA_RESTORE_IPV6_DEFAULT_ROUTE=${MANILA_RESTORE_IPV6_DEFAULT_ROUTE:=True}
 
 # Enable manila services
 # ----------------------