add a finally block to close stderr/stdout

Reference issue: http://tracker.ceph.com/issues/7594
And: http://tracker.ceph.com/issues/9122

this will silence all the horrible Python thread nonsense that occurs after ceph-deploy has closed the remote connection and has nothing else to do.

Users get very confused about this because they think it has to do with something that is breaking in ceph-deploy

Some output that shows how non-internal tracebacks are shown now:

     ceph-deploy disk list node2
     [ceph_deploy.conf][DEBUG ] found configuration file at: /Users/alfredo/.cephdeploy.conf
     [ceph_deploy.cli][INFO  ] Invoked (1.5.11): /Users/alfredo/.virtualenvs/ceph-deploy/bin/ceph-deploy disk list node2
     [node2][DEBUG ] connected to host: node2
     [node2][DEBUG ] detect platform information from remote host
     [node2][DEBUG ] detect machine type
     [ceph_deploy.osd][INFO  ] Distro info: CentOS 6.4 Final
     [ceph_deploy.osd][DEBUG ] Listing disks on node2...
     [node2][DEBUG ] find the location of an executable
     [node2][INFO  ] Running command: sudo /usr/sbin/ceph-disk list
     [node2][DEBUG ] /dev/sda :
     [node2][DEBUG ]  /dev/sda1 other, ext4, mounted on /
     [node2][DEBUG ]  /dev/sda2 other, swap
     [node2][DEBUG ] /dev/sdb other, unknown
     [ceph_deploy][ERROR ] Traceback (most recent call last):
     [ceph_deploy][ERROR ]   File "/Users/alfredo/python/ceph-deploy/ceph_deploy/util/decorators.py", line 65, in newfunc
     [ceph_deploy][ERROR ]     return f(*a, **kw)
     [ceph_deploy][ERROR ]   File "/Users/alfredo/python/ceph-deploy/ceph_deploy/cli.py", line 149, in main
     [ceph_deploy][ERROR ]     return args.func(args)
     [ceph_deploy][ERROR ]   File "/Users/alfredo/python/ceph-deploy/ceph_deploy/osd.py", line 579, in disk
     [ceph_deploy][ERROR ]     disk_list(args, cfg)
     [ceph_deploy][ERROR ]   File "/Users/alfredo/python/ceph-deploy/ceph_deploy/osd.py", line 429, in disk_list
     [ceph_deploy][ERROR ]     raise NameError('welp')
     [ceph_deploy][ERROR ] NameError: welp
     [ceph_deploy][ERROR ]

And internal ones:
     
     (ceph-deploy)papaya ~/tmp/foo ᓆ ceph-deploy disk list node2
     [ceph_deploy.conf][DEBUG ] found configuration file at: /Users/alfredo/.cephdeploy.conf
     [ceph_deploy.cli][INFO  ] Invoked (1.5.11): /Users/alfredo/.virtualenvs/ceph-deploy/bin/ceph-deploy disk list node2
     [node2][DEBUG ] connected to host: node2
     [node2][DEBUG ] detect platform information from remote host
     [node2][DEBUG ] detect machine type
     [ceph_deploy.osd][INFO  ] Distro info: CentOS 6.4 Final
     [ceph_deploy][ERROR ] RuntimeError: internal ceph-deploy error