spdk_shutdown_nvmf_subsystems() was removing the subsystem from the
list, but nvmf_delete_subsystem() also wants to remove it, so drop the
extra removal.
Also rewrite the shutdown loop as a TAILQ_FOREACH_SAFE() to make the
static analyzer happy (and make it more obvious that the loop will
terminate).
Change-Id: Iccadafa77d9cd3e26be21c0f11e62cfc1ef0197c
Signed-off-by: Daniel Verkamp <daniel.verkamp@intel.com>