tests/loadsave: Include common.h in loadsave.c

Signed-off-by: Sasha Kotchubievsky <sashakot@mellanox.com>
Signed-off-by: Hal Rosenstock <hal@mellanox.com>
tests/loadsave: Use CFLAGS instead of CPPFLAGS

C-source uses CFLAGS in compilation and not CPPFLAGS

Signed-off-by: Sasha Kotchubievsky <sashakot@mellanox.com>
Signed-off-by: Hal Rosenstock <hal@mellanox.com>