Make node SSH timeout configurable.

* nodepool/nodepool.py: Make the initial ssh timeout configurable
(retain default of 60 seconds). Looking at the logs there is a very high
occurence of SSH timeout from our providers. Making this timeout
configurable will allow us to adjust the timeout if necessary.
Additionally, fix the comparison between old and new provider configs,
some items were not compared when they should be.

Change-Id: I51df708cb24e93e87c2fedf36d1f9de2131c76bd
Merge "Make node SSH timeout configurable."