fixed detection of server version in cmd client similar to gui client:

fixed detection of server version in cmd client similar to gui client:

first check status.php for version and then capabilities, only use version string if not empty

this also fixes 'File names containing the character ":" are not supported on this file system.' errors in nextcloudcmd (on Linux): The invalidFilenameRegex was set to a static default in case the server version was not set correctly. As newer versions of nextcloud do not return the version in capabilities but status.php, the server version was empty.

Signed-off-by: Patrick Cernko <errror@errror.org>