LU-1907 build: avoid function resolution mistakes by Coverity

LU-1907 build: avoid function resolution mistakes by Coverity

Remove function resolution mistakes made by Coverity version
6.0.3.
The .hs_keycmp function is incorrectly resolved by Coverity,
making the variable passed as its first 'key' parameter to
be considered of the wrong type. Data structures being of
different sizes, it ends up with this Coverity defect:
Out-of-bounds access (OVERRUN_STATIC)
Overrunning static array by passing it as an argument to a
function which indexes it at a higher byte position.

Signed-off-by: Sebastien Buisson <sebastien.buisson@bull.net>
Change-Id: Ia64d90f2faed17981cc4b4eaa960a797ab056daf
Reviewed-on: http://review.whamcloud.com/3955
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Keith Mannthey <keith@whamcloud.com>
Reviewed-by: Bob Glossman <bob.glossman@intel.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>