LU-278 build: Only warn for tag/version mismatch

LU-278 build: Only warn for tag/version mismatch

The configure process should NOT abort just because the most
recent tag is not of the form that upstream uses to tag Lustre.
Downstream developers may use their own tags, or just add
extensions to upsteam's version tags.

Change-Id: I43b63e8438cc37588d5a5b91677102ded22917fb
Signed-off-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-on: http://review.whamcloud.com/1105
Tested-by: Hudson
Reviewed-by: Johann Lombardi <johann@whamcloud.com>