docs: add qemu-storage-daemon(1) man page

docs: add qemu-storage-daemon(1) man page

Document the qemu-storage-daemon tool. Most of the command-line options
are identical to their QEMU counterparts. Perhaps Sphinx hxtool
integration could be extended to extract documentation for individual
command-line options so they can be shared. For now the
qemu-storage-daemon simply refers to the qemu(1) man page where the
command-line options are identical.

Signed-off-by: Stefan Hajnoczi <[email protected]>
Message-Id: <20201209103802[email protected]>
Signed-off-by: Kevin Wolf <[email protected]>