limit WEBSERVICE to http[s] protocols

limit WEBSERVICE to http[s] protocols

and like excel...

'For protocols that aren’t supported, such as ftp:// or file://, WEBSERVICE
returns the #VALUE! error value.'

Change-Id: I0e9c6fd3426fad56a199eafac48de9b0f23914b3
Reviewed-on: https://gerrit.libreoffice.org/47776
Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Markus Mohrhard <markus.mohrhard@googlemail.com>
(cherry picked from commit a916fc0c0e0e8b10cb4158fa0fa173fe205d434a)

Gbp-Pq: Name WEBSERVICE-DDE.diff