Improvement of systemd unit file. Postgresql service should be started after network is up.

The Postgresql server listening on IP address cant be started without properly
started network service.
network.target doesn't check whether network is up
Resolves: rhbz#2127534 and rhbz#2157651
upstream also adopt such change by commit https://git.postgresql.org/gitweb/?p=pgrpms.git;a=commit;h=b0d12f55ba4e0301137e51f7cda1f6ceb1448cd6

Author: fila43

postgresql.service.in

@@ -6,7 +6,8 @@
 
 [Unit]
 Description=PostgreSQL database server
-After=network.target
+# We should start postgresql service after network is up (rhbz#2127534 and rhbz#2157651)
+After=network-online.target
 
 [Service]
 Type=notify