dhclient: T6667: Added workaround for communication with FRR

To increase the chance for dhclient to configure routes in FRR, added a
workaround. Now 10 attempts are performed with 1 second delay and only after
this dhclient gives up.

src/etc/dhcp/dhclient-enter-hooks.d/03-vyos-ipwrapper

@@ -72,6 +72,22 @@ function delroute () {
     fi
 }
 
+# try to communicate with vtysh
+function vtysh_conf () {
+    # perform 10 attempts with 1 second delay for retries
+    for i in {1..10} ; do
+        if vtysh  -c "conf t" -c "$1" ; then
+            logmsg info "Command was configured successfully via vtysh: \"$1\""
+            return 0
+        else
+            logmsg info "Failed to send command to vtysh, retrying in 1 second"
+            sleep 1
+        fi
+    done
+    logmsg error "Failed to configure command via vtysh after 10 attempts: \"$1\""
+    return 1
+}
+
 # replace ip command with this wrapper
 function ip () {
     # pass comand to system `ip` if this is not related to routes change
@@ -84,7 +100,7 @@ function ip () {
             delroute ${@:4}
             iptovtysh $@
             logmsg info "Sending command to vtysh"
-            vtysh -c "conf t" -c "$VTYSH_CMD"
+            vtysh_conf "$VTYSH_CMD"
         else
             # add ip route to kernel
             logmsg info "Modifying routes in kernel: \"/usr/sbin/ip $@\""