Simplify logic for stopping the server in configure-tde-server.sh

I run multiple instances of PostgreSQL on my machine so I would rather
not have it rely on using pgrep to detect if the server is running.

To make this new code more reliable we add set -e so the script aborts
directly e.g. if the port is already in use.

ci_scripts/configure-tde-server.sh

@@ -1,4 +1,6 @@
 #!/bin/bash
+set -e
+
 # This script is used to configure a TDE server for testing purposes.
 export TDE_MODE=1
 
@@ -10,16 +12,11 @@ cd "$SCRIPT_DIR/.."
 export PATH=$INSTALL_DIR/bin:$PATH
 export PGDATA=$INSTALL_DIR/data
 
-if pgrep -x "postgres" > /dev/null; then
-    pg_ctl -D "$PGDATA" stop
-fi
-
-if pgrep -x "postgres" > /dev/null; then
-    echo "Error: a postgres process is already running"
-    exit 1
-fi
-
 if [ -d "$PGDATA" ]; then
+    if pg_ctl -D "$PGDATA" status >/dev/null; then
+        pg_ctl -D "$PGDATA" stop
+    fi
+
     rm -rf "$PGDATA"
 fi