Bug 636300

Description of problem:
There are two subproblems:
A. username can be optionally defined twice (per device instance and per node) while this ability to define the same parameter on both places is:
  - unique across Luci (this should be presently the only such case which can be strange to the user)
  - not necessary (it does not make much sense to define it twice, although
    optionally)
(note: per-node username setting does not even work, but at least, user is offered with setting it on this place)
B. according to the code of fence_egenera, the key parameter to set username is "user", but Luci uses "username" (related problem is missing information about how to set username in fence_egenera man page, see bug #635824)

Version-Release number of selected component (if applicable):
luci-0.22.2-14.el6.x86_64

How reproducible:
Always.

Steps to Reproduce (how to input username information twice while the incorrect parameter "username" instead of "user" is used):
1. go to "Fence Devices", select Add, choose the Egenera device
2. *now you can set also username*, do it and when other fields are filled, submit the form
3. now go "Nodes" tab, click on certain node, in its details add a fencing method (if no one currently present), from within this method, click "Add a Fence Instance", here, select just added fence device instance
4. *now you can set also username*, do it (although this one will not be propagated to the cluster.conf as mentioned in description)
  
Actual results:
Username setting was shown on two different places and cluster.conf contains something like this:

(...)
        <clusternode name="node1" nodeid="1" votes="1">
                <fence>
                        <method name="test_method">
                                <device name="test_egenera"/>
                        </method>
                </fence>
        </clusternode>
(...)
<fencedevices>
        <fencedevice agent="fence_egenera" cserver="localhost" name="test_egenera" username="username_global"/>
</fencedevices>


Expected results:
Username setting was shown only at on place (presumably in per device instance configuration) and in the parameter "user" was used instead of "username", i.e. cluster.conf from above should look like this:

(...)
        <clusternode name="node1" nodeid="1" votes="1">
                <fence>
                        <method name="test_method">
                                <device name="test_egenera"/>
                        </method>
                </fence>
        </clusternode>
(...)
<fencedevices>
        <fencedevice agent="fence_egenera" cserver="localhost" name="test_egenera" user="username_global"/>
</fencedevices>


Additional info:
To verigy the fix, no Egenera hardware should be needed, checking Luci interactively and watching cluster.conf should be enough.