add support for server set metadata item

add set_meta_item to the servers python API as specified by the 1.1 API

Change-Id: I01c92cde18656b23b45aedd41c50d3a474d91435
Fixes ambiguous cli output between "None" and NoneType

Print hyphen(-) in python client output when attribute value is not
set(NoneType) so that it is distinguishable between "None" string
and NoneType value.

Change-Id: I5ec0f39f13aca45fa95ddb59472c20207c63bf91
Closes-Bug: #1266414
shell: refactor boot to use _print_server

In the shell command when we use the command boot, at the end
we use code to print some server information.
We should use the already defined function _print_server.

Change-Id: I133d7706458c71974ba464ab686cf3679a562592
Closes-Bug: #1265534
Removes use of timeutils.set_time_override

The set_time_override function in timeutils was written as a
helper function to mock utcnow for unittests before 'mock' was
generally used. Now that we have mock and fixture, we no longer
need to use it.

Change-Id: I809825560b0324498010bd93aa1ceef552554375
Partial-Bug: #1266962
Merge "shell: refactor boot to use _print_server"
Merge "add support for server set metadata item"
Merge "Fixes ambiguous cli output between "None" and NoneType"
Merge "Removes use of timeutils.set_time_override"