env: fix build break on pre-6.4 RHEl/CentOS boxes
env: fix build break on pre-6.4 RHEl/CentOS boxes

Let's just hardcode these fallocate flags if falloc.h is too old. The kernel
will return EOPNOTSUPP, which we have to deal with anyway.

Change-Id: Ie472382ac19f0d3543bc5e0b2509374ff3ace277
Reviewed-on: http://gerrit.sjc.cloudera.com:8080/4819
Reviewed-by: David Alves <33ea948168c114d220e0372a903be6ee60f6396e@cloudera.com>
Reviewed-by: Alex Feinberg <befd6aa234c2f4cc93d21d7577c06d8f75d6f7de@cloudera.com>
Tested-by: jenkins

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