Ceph slow rebalance

When you need to make big change to a crush map you want to reset some ceph config to make sure that the tenant traffic is favored over the rebalance traffic. By setting 
```
default['bcpc']['ceph']['rebalance'] = true
```
it will make the following config changes 
```
 paxos_propose_interval = 60 
 osd_recovery_max_active = 1
 osd_max_backfills  = 1
 osd_op_threads = 10    
 osd_recovery_op_priority = 1
 osd_mon_report_interval_min = 30         
```

The recipes will set the ceph.conf to reflect those changes and do a dynamic configuration of the ceph daemons via the admin sockets. 

In addition it will set `no scrub` and `nodeep-scrub` flags which will stop any running scrub operations. 

when you are done making changes you should set 
```
default['bcpc']['ceph']['rebalance'] = false
```
and rechef the entire cluster.