librspreload: Fix typecast to eliminate compile warnings

src/preload.c: In function ?bind?:
src/preload.c:350: warning: assignment from incompatible pointer type
src/preload.c: In function ?connect?:
src/preload.c:397: warning: assignment from incompatible pointer type

Signed-off-by: Hal Rosenstock <hal@mellanox.com>
Signed-off-by: Sean Hefty <sean.hefty@intel.com>