Harden version checking for boto

Simple string comparison is not effective for version checking.
Let's switch to using pkg_resources.parse_version and compare
the tuples. Per review feedback, enabling the code path for
2.13 as well. Originally we had handled this by excluding
2.13 from requirements. With this we should be able to removing
the exclusion for 2.13 from global requirements.

Change-Id: Ie047f7201d8e6a9a9641000d387c4312506f49b1
Closes-Bug: #1239220
Merge "Harden version checking for boto"