s3: smbd: Fix cosmetic bug logging pathnames from Linux kernel clients using SMB1 DFS calls.

The Linux kernel SMB1 client has a bug - it sends
DFS pathnames as:

\\server\share\path

instead of:

\server\share\path

Causing us to mis-parse server,share,remaining_path here
and jump into 'goto local_path' at 'share\path' instead
of 'path'.

This doesn't cause an error as the limits on share names
are similar to those on pathnames.

parse_dfs_path() which we call before filename parsing
copes with this by calling trim_char on the leading '\'
characters before processing.

Do the same here so logging of pathnames looks better.

How did I find this ? Lots and lots of manual
testing with the Linux kernel client to make
sure all the recent changes haven't broken Linux
SMB1/2/3 DFS :-).

BUG: https://bugzilla.samba.org/show_bug.cgi?id=15144

Signed-off-by: Jeremy Allison <jra@samba.org>
Reviewed-by: Ralph Boehme <slow@samba.org>
