PHYP: Adding network interface

PHYP: Adding network interface

This is the implementation of the previous patch now using virInterface*
API. Ended up this patch got much more simpler, smaller and easier to
review. Here is some details:

  * MAC size and interface name are fixed due to specifications on HMC,
    both are created automatically and CAN'T be specified from user. They
    have the following format:

     * MAC: 122980003002
     * Interface name: U9124.720.067BE8B-V3-C0

  * I did replaced all the |grep|sed following the comments Eric Blake
    did on the last patch.

  * According to my last email, It's not possible to create a network
    interface without assigning it to a specific lpar. Then, I am using
    this very minimalistic XML file for testing:

     <interface type='ethernet' name='LPAR01'>
     </interface>

    In this file I am using "name" as the lpar name which I am going to
    assign the new network interface. I couldn't find a better way to
    refer to it. Comments are welcome.

  * Regarding the fact I am sleeping one second waiting for the HMC to
    complete creation of the interface, I don't have means to check
    if the whole process is done. All I do is execute a command, wait
    until is complete (which is not enough in this case) check
    the return and the exit status. The process of actually creating
    a networking interface seems to take a little longer than just the
    return of the ssh control.