Run the dnspython dependency back.

The initial dnspython dependency was probably a bit aggressive.  Ubuntu
Oneiric and Precise both packaged 1.9.4 and there's not too much in the
package changelog to recommend 1.10.0 over 1.9.4, at least not for a
requirement.

Change-Id: I8e2a03e4a89ee0f36c860cdaf21a7a0fea1709ca
Merge "Run the dnspython dependency back."