This is a followup to https://review.openstack.org/#/c/541609/ that
changes most outstanding direct uses of sys.stdout to use the encoded
stdout set up by cliff.

Change-Id: I07cfc418385fc787d3b7d3c32d39676cf81bb91f

Support Neutron network mtu configuration with a new argument, --mtu
that allows CLI users to set MTU for Neutron networks.

Change-Id: I93d23581c7e8c84eaf9bb3b293360036f60f456b

Change-Id: If77609d06e7d80c8da5111b8a30036b58fbfa187

a)

/os-floating-ips was removed in Compute API 2.36 and from novaclient's
Python API in 10.0

Add to api.computev2:
floating_ip_add()
floating_ip_remove()

Convert add floating IP command to nova-net/neutron split:
"server add floating ip"
"server remove floating ip"

b)

/os-hosts was removed in Compute API 2.43 and from novaclient's
Python API in 10.0.

Add to api.computev2:
host_list()
host_set()
host_show()

Convert host commands to use intenal api:
"host list"
"host set"
"host show"

c)

The introduction of the Network-style commands into the server group
broke cliff's autoprogram directive as it executes the get_parser() methods
without fully initializing the Command object.

NOTE: This is really three reviews squashed to get through the gate in one pass.

Depends-on: Id6de87211d6c4ea8fd14aa9203d8d5b17e9e2f04
Change-Id: I5116086f9a9e4b2b31a744bf8f4558c79f0bfe59

When test_server_commands_main_help() fails it dumps a ton of
unformatted text on an exception message. This commit attempts to clean
it up to make it easier to read.

Change-Id: I793e6337728a22302a5a87938dbec60d7f2320d8