Expose user for service configuration for init.d script

Currently we hardcode the user we use to start services. Allow the
user to decided who to use.

Sadly, we cannot support systemd services at this time. We likely need
to switch to the systemd task or write out own logic. We'll have to
revisting this in the future.

Change-Id: I338d167863509667b935ccc7490d796315bc6153
Signed-off-by: Paul Belanger <pabelanger@redhat.com>

files/etc/default/zuul-launcher

@@ -5,3 +5,6 @@
 # The prefix used when zuul-launcher was installed. Be sure to update this value
 # if you are using a virtualenv.
 PREFIX=/usr/local
+
+# The user used to start zuul-launcher service.
+RUNASUSER=zuul

files/etc/default/zuul-merger

@@ -5,3 +5,6 @@
 # The prefix used when zuul-merger was installed. Be sure to update this value
 # if you are using a virtualenv.
 PREFIX=/usr/local
+
+# The user used to start zuul-merger service.
+RUNASUSER=zuul

files/etc/default/zuul-server

@@ -5,3 +5,6 @@
 # The prefix used when zuul-server was installed. Be sure to update this value
 # if you are using a virtualenv.
 PREFIX=/usr/local
+
+# The user used to start zuul-server service.
+RUNASUSER=zuul

files/etc/init.d/zuul-launcher

@@ -17,12 +17,12 @@ DESC="Zuul Launcher"
 NAME=zuul-launcher
 PIDFILE=/var/run/$NAME/$NAME.pid
 SCRIPTNAME=/etc/init.d/$NAME
-USER=zuul
 
 # Read configuration variable file if it is present
 [ -r /etc/default/$NAME ] && . /etc/default/$NAME
 
 DAEMON=$PREFIX/bin/zuul-launcher
+USER=${RUNASUSER:-zuul}
 
 # Exit if the package is not installed
 [ -x "$DAEMON" ] || exit 5

files/etc/init.d/zuul-merger

@@ -17,12 +17,12 @@ DESC="Zuul Merger"
 NAME=zuul-merger
 PIDFILE=/var/run/$NAME/$NAME.pid
 SCRIPTNAME=/etc/init.d/$NAME
-USER=zuul
 
 # Read configuration variable file if it is present
 [ -r /etc/default/$NAME ] && . /etc/default/$NAME
 
 DAEMON=$PREFIX/bin/zuul-merger
+USER=${RUNASUSER:-zuul}
 
 # Exit if the package is not installed
 [ -x "$DAEMON" ] || exit 5

files/etc/init.d/zuul-server

@@ -15,12 +15,12 @@ DESC="Zuul"
 NAME=zuul-server
 PIDFILE=/var/run/$NAME/$NAME.pid
 SCRIPTNAME=/etc/init.d/$NAME
-USER=zuul
 
 # Read configuration variable file if it is present
 [ -r /etc/default/$NAME ] && . /etc/default/$NAME
 
 DAEMON=$PREFIX/bin/zuul-server
+USER=${RUNASUSER:-zuul}
 
 # Exit if the package is not installed
 [ -x "$DAEMON" ] || exit 5