Change boot wait time to 40 seconds

This splits the difference between 60 seconds (from [1]) and the
previous 20 seconds, which is no longer enough time to boot cleanly...

@tomswartz07, @mod, and I have all been experiencing mid-20 second boot
times, so 40 seconds seems like enough headroom without being excessive.

[1]: 443997f

arch-template.json

@@ -18,7 +18,7 @@
             "http_directory": "srv",
             "boot_wait": "5s",
             "boot_command": [
-                "<enter><wait10><wait10><wait10>",
+                "<enter><wait10><wait10><wait10><wait10>",
                 "/usr/bin/curl -O http://{{ .HTTPIP }}:{{ .HTTPPort }}/enable-ssh.sh<enter><wait5>",
                 "/usr/bin/curl -O http://{{ .HTTPIP }}:{{ .HTTPPort }}/poweroff.timer<enter><wait5>",
                 "/usr/bin/bash ./enable-ssh.sh<enter>"
@@ -39,7 +39,7 @@
             "http_directory": "srv",
             "boot_wait": "5s",
             "boot_command": [
-                "<enter><wait10><wait10><wait10>",
+                "<enter><wait10><wait10><wait10><wait10>",
                 "/usr/bin/curl -O http://{{ .HTTPIP }}:{{ .HTTPPort }}/enable-ssh.sh<enter><wait5>",
                 "/usr/bin/curl -O http://{{ .HTTPIP }}:{{ .HTTPPort }}/poweroff.timer<enter><wait5>",
                 "/usr/bin/bash ./enable-ssh.sh<enter>"
@@ -60,7 +60,7 @@
             "http_directory": "srv",
             "boot_wait": "5s",
             "boot_command": [
-                "<enter><wait10><wait10><wait10>",
+                "<enter><wait10><wait10><wait10><wait10>",
                 "/usr/bin/curl -O http://{{ .HTTPIP }}:{{ .HTTPPort }}/enable-ssh.sh<enter><wait5>",
                 "/usr/bin/curl -O http://{{ .HTTPIP }}:{{ .HTTPPort }}/poweroff.timer<enter><wait5>",
                 "/usr/bin/bash ./enable-ssh.sh<enter>"
@@ -79,7 +79,7 @@
             "http_directory": "srv",
             "boot_wait": "5s",
             "boot_command": [
-                "<enter><wait10><wait10><wait10>",
+                "<enter><wait10><wait10><wait10><wait10>",
                 "/usr/bin/curl -O http://{{ .HTTPIP }}:{{ .HTTPPort }}/enable-ssh.sh<enter><wait5>",
                 "/usr/bin/curl -O http://{{ .HTTPIP }}:{{ .HTTPPort }}/poweroff.timer<enter><wait5>",
                 "/usr/bin/bash ./enable-ssh.sh<enter>"