osx: snapview-server fails to build on OSX use 'syscall.h'

Change-Id: Ib9443913abb89c6a04a8723bced4c77128047bd0
BUG: 1130307
Signed-off-by: Harshavardhana <harsha@harshavardhana.net>
Reviewed-on: http://review.gluster.org/8487
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Kaleb KEITHLEY <kkeithle@redhat.com>