It is always set to nvmf_process_async_completion and is only used
within the library.
Also rename nvmf_process_async_completion to spdk_nvmf_request_complete
to clarify its purpose.
Change-Id: Ie737fb60688329bfe329a8553c4a40ff2e5f8f1d
Signed-off-by: Daniel Verkamp <daniel.verkamp@intel.com>