Remove 'can_failover' for newer sentinel

```
Mixlib::ShellOut::ShellCommandFailed
------------------------------------
Expected process to exit with [0], but received '1'
---- Begin output of /sbin/service redis-sentinel-sentinel start ----
STDOUT: Starting Redis sentinel...
STDERR: *** FATAL CONFIG FILE ERROR ***
Reading the configuration file, at line 4
>>> 'sentinel can-failover server yes'
Unrecognized sentinel configuration statement.
---- End output of /sbin/service redis-sentinel-sentinel start ----
Ran /sbin/service redis-sentinel-sentinel start returned 1
```



can-failover does not exist anymore in the newer sentinel versions