Change master in XenServer Pool

If actual master is online

Disable HA if enabled:
```
xe pool-ha-disable
```
get uuid of hosts
```
xe host-list
```
Look for uuid of member server you want to make as new master server

change master

xe pool-designate-new-master host-uuid=<new-master-uuid>

If HA was enabled, restart HA
```
xe pool-ha-enable
```

If pool master is offline/dead

on new master server
```
xe pool-emergency-transition-to-master
```
recover member server
```
xe pool-recover-slaves
```

Authors:

Jochen Schnuerle