ftp: fix CKSM command for files with white-space

The CKSM command allows a client to request the checksum of a
file.  It assumes that the path contains no whitespace and fails
any request where this isn't true.

This patch fixes this.

Target: master
Patch: http://rb.dcache.org/r/6853/
Acked-by: Gerd Behrmann
Request: 2.8
Request: 2.7
Request: 2.6
ftp: add work-around for GlobusOnline uploads

The GlobusOnline client expects that the MD5 checksum is available
after uploading the file and does not degrade gracefully if an
alternative checksum is supplied.

This patch adds support where, if the GO client identifies itself,
then the pool is requested to generate an MD5 checksum.

Target: master
Patch: http://rb.dcache.org/r/6853
Acked-by: Gerd Behrmann