Description of problem:

When the disk is removed from the VM, we get these logs from glusterfsd(brick process)

```
Broadcast message from systemd-journald@node1 (Mon 2017-03-27 12:14:29 UTC):

var-lib-heketi-mounts-vg_3dc59eba73cb2070a96c0fec5a2b5e82-brick_455ecb9f475cf6bd7dd201457799736c-brick[14090]: [2017-03-27 12:14:29.751829] M [MSGID: 113075] [posix-helpers.c:1841:posix_health_check_thread_proc] 0-vol_71bda80b7a159f08ad795e4f4f244bd4-posix: health-check failed, going down


Message from syslogd@localhost at Mar 27 12:14:29 ...
 var-lib-heketi-mounts-vg_3dc59eba73cb2070a96c0fec5a2b5e82-brick_455ecb9f475cf6bd7dd201457799736c-brick[14090]:[2017-03-27 12:14:29.751829] M [MSGID: 113075] [posix-helpers.c:1841:posix_health_check_thread_proc] 0-vol_71bda80b7a159f08ad795e4f4f244bd4-posix: health-check failed, going down
```

When the kill signal is sent to the same brick process as part of replace-brick, we get 

```
Broadcast message from systemd-journald@node1 (Mon 2017-03-27 12:14:59 UTC):

var-lib-heketi-mounts-vg_3dc59eba73cb2070a96c0fec5a2b5e82-brick_455ecb9f475cf6bd7dd201457799736c-brick[14090]: [2017-03-27 12:14:59.752367] M [MSGID: 113075] [posix-helpers.c:1847:posix_health_check_thread_proc] 0-vol_71bda80b7a159f08ad795e4f4f244bd4-posix: still alive! -> SIGTERM


Message from syslogd@localhost at Mar 27 12:14:59 ...
 var-lib-heketi-mounts-vg_3dc59eba73cb2070a96c0fec5a2b5e82-brick_455ecb9f475cf6bd7dd201457799736c-brick[14090]:[2017-03-27 12:14:59.752367] M [MSGID: 113075] [posix-helpers.c:1847:posix_health_check_thread_proc] 0-vol_71bda80b7a159f08ad795e4f4f244bd4-posix: still alive! -> SIGTERM
Shared connection to 192.168.21.14 closed.
```

It is found that glusterd has crashed on the system and the system goes to emergency mode.


This might not be the best way to test, if a better way proves that gluster is resilient to disk crashes, this bug might be closed.