heartbeat_interval template var is missing

[scorpp]

Master instance starts fine.
When running a slave using command form readme it fails after executing heartbeat command:

# docker run --rm --name postgresql-slave -e PG_DEPLOYMENT_TYPE=replicated -e PG_ROLE=slave -e PG_WAL_LEVEL=hot_standby -e PG_MAER_HOST=192.168.122.55 -p 5432:5432/tcp bettervoice/postgresql-container:9.3 
Creating new cluster 9.3/main ...
  config /etc/postgresql/9.3/main
  data   /var/lib/postgresql/9.3/main
  locale C
  port   5432
transaction log start point: 0/4000028 on timeline 1
transaction log end point: 0/40000F0
pg_basebackup: base backup completed
 * Starting PostgreSQL 9.3 database server
   ...done.
PING 192.168.122.55 (192.168.122.55) 56(84) bytes of data.
64 bytes from 192.168.122.55: icmp_seq=1 ttl=63 time=0.227 ms
64 bytes from 192.168.122.55: icmp_seq=2 ttl=63 time=0.206 ms
64 bytes from 192.168.122.55: icmp_seq=3 ttl=63 time=0.208 ms

--- 192.168.122.55 ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2005ms
rtt min/avg/max/mdev = 0.206/0.213/0.227/0.019 ms
Traceback (most recent call last):
  File "/usr/bin/heartbeat", line 19, in <module>
    monitor()
  File "/usr/bin/heartbeat", line 16, in monitor
    time.sleep()
TypeError: sleep() takes exactly 1 argument (0 given)
Traceback (most recent call last):
  File "/usr/bin/start-postgres", line 198, in <module>
    run('heartbeat')
  File "/usr/bin/start-postgres", line 130, in run
    check_call([app] + list(args))
  File "/usr/lib/python2.7/subprocess.py", line 540, in check_call
    raise CalledProcessError(retcode, cmd)
subprocess.CalledProcessError: Command '['heartbeat']' returned non-zero exit status 1

Issue caused by last commit where HEARTBEAT_INTERVAL env var was removed and corresponding heartbeat_interval template var as well.