Add method delete_all_nics to vm.py

[dwettstein]

This PR adds the method delete_all_nics to vm.py. The logic is basically the same as in the delete_nic method, except that instead of deleting just the NIC with given index, it deletes all.

NOTE: I have not added a dedicated test for this method, because of the same reason as above.

PS: I recommend to merge also PR #720, as it contains some bugfixes for delete_nic method.

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This change is 

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[rocknes]

Reviewable status: 0 of 1 files reviewed, 1 unresolved discussion (waiting on @dwettstein and @rocknes)

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pyvcloud/vcd/vm.py, line 757 at r1 (raw file):

                net_conn_section.remove(nc)
        else:
            raise InvalidStateException(

I think we don't need to raise an exception if no nics are found.

[dwettstein]

Reviewable status: 0 of 1 files reviewed, 1 unresolved discussion (waiting on @rocknes)

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pyvcloud/vcd/vm.py, line 757 at r1 (raw file):

Previously, rocknes wrote…

I think we don't need to raise an exception if no nics are found.

Thanks @rocknes, you're right, I have removed the else part.

[dwettstein]

Hi @rocknes

I have implemented your requested changes. Is there something left to do for this PR?

Thanks.