LU-279 tests: Ensure lgetxattr is consistent

LU-279 tests: Ensure lgetxattr is consistent

* Added the lgetxattr_size_check.c program to compare the size returned
  by lgetxattr() when passed zero size buffers and non zero size buffers
* Sanity test 17l was added to make use of this new test program and
  ensure that the values returned by lgetxattr remain consistent

Signed-off-by: Prakash Surya <surya1@llnl.gov>
Change-Id: Id46dbe888d42b058e02ec32b6d1612705d7f6349
Reviewed-on: http://review.whamcloud.com/547
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Fan Yong <fan.yong@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>