refactor(master.cfg): convert list of strings to multiline strings

buildbot/master/master.cfg

@@ -33,23 +33,23 @@ c['caches'] = {
 ####### BUILDSLAVES
 
 def make_user_data(s):
-    lines = []
-    lines.append("#!/bin/bash")
-    lines.append("add-apt-repository -y ppa:saltstack/salt")
-    lines.append("apt-get update")
-    lines.append("apt-get -y install python-pip salt-minion")
-    lines.append("echo 96.126.125.232 salt >> /etc/hosts")
-    lines.append("echo %s > /etc/salt/minion_id" % s)
-    lines.append("cat <<EOF > /etc/salt/pki/minion/minion.pem")
-    lines.append(MINION_PRIVATE_KEY.strip())
-    lines.append("EOF")
-    lines.append("cat <<EOF > /etc/salt/pki/minion/minion.pub")
-    lines.append(MINION_PUBLIC_KEY.strip())
-    lines.append("EOF")
-    lines.append("service salt-minion restart")
-    lines.append("sleep 5")
-    lines.append("salt-call state.highstate")
-    return "\n".join(lines)
+    return """\
+#!/bin/bash
+add-apt-repository -y ppa:saltstack/salt
+apt-get update
+apt-get -y install python-pip salt-minion
+echo 96.126.125.232 salt >> /etc/hosts
+echo %(s)s > /etc/salt/minion_id
+cat <<EOF > /etc/salt/pki/minion/minion.pem
+%(private_key)s
+EOF
+cat <<EOF > /etc/salt/pki/minion/minion.pub
+%(public_key)s
+EOF
+service salt-minion restart
+sleep 5
+salt-call state.highstate""" % \
+    {'private_key': MINION_PRIVATE_KEY.strip(), 'public_key':  MINION_PUBLIC_KEY.strip(), 's': s}
 
 c['slaves'] = []
 for s in MAC_SLAVES + ANDROID_SLAVES + HEAD_SLAVES + LINUX_LINODE_SLAVES: