LU-5252 hsm: llapi_hsm_event_fd is local, so make it static.

LU-5252 hsm: llapi_hsm_event_fd is local, so make it static.

This is a backport to b2_5.

Lustre-change: http://review.whamcloud.com/10808
Lustre-commit: 9feb80c65b077204f7091e90f314098266fb7e82

Change-Id: I9905d0251702a11a9c2546ba4bd78fd00658d28a
Signed-off-by: Frank Zago <fzago@cray.com>
Signed-off-by: James Nunez <james.a.nunez@intel.com>
Signed-off-by: Jian Yu <jian.yu@intel.com>
Reviewed-on: http://review.whamcloud.com/11362
Reviewed-by: John L. Hammond <john.hammond@intel.com>
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>