more dockerization work

[From @joshdata: This is part of @toilal's work in #377 and 1eb77c332b. The changes are:

* Separates out the runit configuration from starting Mail-in-a-Box setup so that Mail-in-a-Box setup does not block the starting of runit services and we can assume that runit is running during setup (i.e. we can restart services).
* Adds a SKIP_INSTALL flag so that the container can be restarted without re-running the whole Mail-in-a-Box setup.
* Made containers/docker/run more flexible.
* I'm also adding some "|| exit 0"s to the run script to stop if there are any docker errors.
* I'm also adding the prereqs installs from questions.sh into Dockerfile so we don't have to reinstall each time.

]

setup/dns.sh

@@ -127,6 +127,8 @@ EOF
 chmod +x /etc/cron.daily/mailinabox-dnssec
 
 # Permit DNS queries on TCP/UDP in the firewall.
-
 ufw_allow domain
 
+# Start nsd. None of the zones are configured until the management daemon is
+# run later, though.
+restart_service nsd

setup/functions.sh

@@ -167,19 +167,17 @@ function ufw_allow {
 }
 
 function restart_service {
-	# Restart a service quietly.
+	if [ -z "$IS_DOCKER" ]; then
+		# Restart the service.
+		hide_output service $1 restart
 
-	if [[ ! -z "$IS_DOCKER" && "$1" == "dovecot" ]]; then
-		# In Docker, sysvinit takes care of any services with an init.d
-		# script. The dovecot package provides an Upstart config only,
-		# and so it won't work this way. We make a new script for it
-		# elsewhere. We also cant do `sv restart dovecot` because runit
-		# is not running until after the setup scripts are run. So we
-		# will have to skip starting dovecot for now.
-		return 0
+	else
+		# In Docker, make sure the service is not disabled by a down file.
+		if [ -f /etc/service/$1/down ]; then
+			rm /etc/service/$1/down
+		fi
+		sv restart $1
 	fi
-
-	hide_output service $1 restart
 }
 
 ## Dialog Functions ##

setup/owncloud.sh

@@ -184,4 +184,5 @@ chmod +x /etc/cron.hourly/mailinabox-owncloud
 
 # Enable PHP modules and restart PHP.
 php5enmod imap
+restart_service memcached
 restart_service php5-fpm

setup/questions.sh

@@ -12,8 +12,10 @@ if [ -z "$NONINTERACTIVE" ]; then
 		apt_get_quiet install dialog python3 python3-pip  || exit 1
 	fi
 
+	if [ -z "$IS_DOCKER" ]; then
 	# email_validator is repeated in setup/management.sh
 	hide_output pip3 install "email_validator==0.1.0-rc5" || exit 1
+	fi
 
 	message_box "Mail-in-a-Box Installation" \
 		"Hello and thanks for deploying a Mail-in-a-Box!

setup/start.sh

@@ -102,14 +102,6 @@ source setup/zpush.sh
 source setup/management.sh
 source setup/munin.sh
 
-# In Docker, sysvinit services are started automatically. Runit services
-# aren't started until after this setup script finishes. But we need
-# Dovecot (which is Upstart-only) running in order to create the first
-# mail user. So start dovecot now.
-if [ ! -z "$IS_DOCKER" ]; then
-	/usr/sbin/dovecot -c /etc/dovecot/dovecot.conf
-fi
-
 # Ping the management daemon to write the DNS and nginx configuration files.
 until nc -z -w 4 localhost 10222
 do