The env layer already understands that shm_id < 0 means that
multi-process is not enabled. Leave shm_id defaulted to -1 so that
other code can detect when it is not set.
Change-Id: Ifd1667598d55c216f95f13561dc2a550677db5f4
Signed-off-by: Daniel Verkamp <daniel.verkamp@intel.com>