Fix settings update in juju-core.

Fix settings update in juju-core.

When sending ServiceSet requests, the GUI included
a Config parameter where juju-core expects an
Option one. 

Also fixed the parameter name used in ServiceSetYAML.

QA:
- deploy and expose the GUI in a juju-core env;
- switch to this branch: 
    juju set juju-gui juju-gui-source=lp:~frankban/juju-gui/service-set-simple
- try to change settings (e.g. juju-gui-debug);
- refresh.

The settings viewlet should reflect the changes and,
after a while (after the config-changed hook execution), 
the new settings should be applied.

https://code.launchpad.net/~frankban/juju-gui/service-set-simple/+merge/187567

(do not edit description out of merge proposal)

[frankban, 2013-09-25 17:12:18]

Please take a look.

[jeff.pihach, 2013-09-26 14:44:57]

QA NO GOOD

Using the charm: cs:precise/juju-gui-76
I switch to your branch
I click the toggle for 'juju-gui-console-enabled'
I then click 'Save'
All of the other configuration value inputs are emptied out
Refreshing shows that my config was saved however.

[jeff.pihach, 2013-09-26 15:20:30]

LGTM QA Ok after investigation of the issue (preexisting)
Thanks!!

[frankban, 2013-09-26 15:27:33]

*** Submitted:

Fix settings update in juju-core.

When sending ServiceSet requests, the GUI included
a Config parameter where juju-core expects an
Option one. 

Also fixed the parameter name used in ServiceSetYAML.

QA:
- deploy and expose the GUI in a juju-core env;
- switch to this branch: 
    juju set juju-gui juju-gui-source=lp:~frankban/juju-gui/service-set-simple
- try to change settings (e.g. juju-gui-debug);
- refresh.

The settings viewlet should reflect the changes and,
after a while (after the config-changed hook execution), 
the new settings should be applied.

R=jeff.pihach
CC=
https://codereview.appspot.com/13917043