uipc_shm: Fix double check for shmfd->shm_path

[ricardobranco777]

Fix double check for shmfd->shm_path != NULL

[gmshake]

Looks good to me.

[emaste]

Looks like this used to have double-checked locking:

9696feebe2320 (John Baldwin            2014-09-22 16:20:47 +0000 1088)  if (shmfd->shm_path != NULL) {
9696feebe2320 (John Baldwin            2014-09-22 16:20:47 +0000 1089)          sx_slock(&shm_dict_lock);
9696feebe2320 (John Baldwin            2014-09-22 16:20:47 +0000 1090)          if (shmfd->shm_path != NULL)

The lock was removed in 56d0e33

[emaste]

Looks good, one style(9) nit that can be cleaned up now that there's less indentation

[emaste]

Pushed as 7975f57

[bsdimp]

Hmmm, OK. pushing after the fact definitely doesn't work to get to merged.