scripts: fix dcache script for Solaris machines

Patch http://rb.dcache.org/r/6293/ (committed as 19c2b522)
fixed a problem with the configuration cache not being
invalidated.

Unfortunately, in fixing a Mac-specific issue, the patch
introduced a Solaris-specific issue; specifically, that
Solaris machines do not support any options to the hostname
command.  The result is that calls like 'hostname -s' will
set the hostname to '-s'.

This patch fixes the problem by using shell's built in
filtering.

Target: master
Ticket: https://github.com/dCache/dcache/issues/335
Request: 2.7
Request: 2.6
Request: 2.2
Patch: http://rb.dcache.org/r/6315/
Acked-by: Gerd Behrmann