Fix postgres errors in Travis CI again.

Travis CI's model of installing every version of postgres on the test
VM and then shutting all the versions other than the one requested
down seems to not work very well with doing apt upgrades.  It seems
the best way to resolve this is to just uninstall the versions we
don't need.

tools/travis/production-helper

@@ -9,14 +9,9 @@ ln -s /etc/ssl/private/ssl-cert-snakeoil.key /etc/ssl/private/zulip.key
 tar -xf zulip-server-travis.tar.gz
 mv zulip-server-travis /root/zulip
 
+# Do an apt upgrade to start with an up-to-date machine
 export APT_OPTIONS="-o Dpkg::Options::=--force-confdef -o Dpkg::Options::=--force-confold"
-
-# Make sure we've done an apt upgrade and then stop postgres to
-# workaround problems with Travis CI having multiple postgres versions
-# installed on the system and 9.1 starting up and conflicting with
-# running 9.3 later.
 apt-get upgrade -y $APT_OPTIONS
-service postgresql stop
 # Install Zulip
 /root/zulip/scripts/setup/install
 

tools/travis/setup-production

@@ -2,6 +2,11 @@
 set -e
 set -x
 
+# Uninstall the unnecessary extra versions of postgres that Travis CI
+# installs since if we don't do this, doing apt upgrades can fail due
+# to conflicts over which version of postgres should be running.
+sudo apt-get remove postgresql-9.1 postgresql-9.2 postgresql-9.4 -y
+
 pip install pbs
 python provision.py --travis
 source /srv/zulip-venv/bin/activate