LU-1912 tests: check Lustre version in generate_db()

LU-1912 tests: check Lustre version in generate_db()

We need to check Lustre version to make sure the test for
new fixup does not run on unsupported Lustre version.

Signed-off-by: Yu Jian <yujian@whamcloud.com>
Change-Id: I6fe5f31dc0ab5ec32879fc0a08216365fee45176
Reviewed-on: http://review.whamcloud.com/4021
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Wei Liu <sarah@whamcloud.com>
Reviewed-by: Minh Diep <mdiep@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>