LU-11848 tests: handle 4-digit version numbers properly

LU-11848 tests: handle 4-digit version numbers properly

Allow version_code() to handle and compare 4-digit version numbers
properly.

Signed-off-by: Andreas Dilger <adilger@whamcloud.com>
Change-Id: I8f57537f87bb1c087def277d0d6192def43ebbe5
Reviewed-on: https://review.whamcloud.com/40897
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Bobi Jam <bobijam@hotmail.com>
Reviewed-by: James Nunez <jnunez@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>