xfsprogs: libxcmd: kill "search" arg in fs_device_number()

xfsprogs: libxcmd: kill "search" arg in fs_device_number()

The function fs_device_number() in libxcmd allows the caller to
optionally "search" in /dev for a given device path in order to look
up the dev_t that represents that device path.

If set, all that function does is prepend "/dev/" to the path to see
if that produces a device path that works.  So it appears this might
have been to support providing just the basename of a device as a
shorthand for its full path.

In practice, the paths passed to this function with "search" set are
those used in the mount options for a mounted XFS filesystem for the
optional log and real-time device paths.  When such paths are used
in the XFS mount path, they will have been subject to a AT_FDCWD
path lookup, so unless the process mounting the filesystem was
sitting in /dev no relative path would ever be specified as just the
basename.

Even though the "mounting with CWD=/dev" is a conceivable scenario,
I think it is not likely enough to warrant the special handling to
cover that case in fs_device_number().

So delete the code that retries with a "/dev" prepended, eliminate
the "search" argument that enables it, and fix the callers
accordingly.

Signed-off-by: Alex Elder <aelder@sgi.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>