[BUGFIX] "Show page" does not use a proper URL scheme

"Show page" context menu and Web>View do not use proper scheme if
that is set in the page properties. They always use the scheme of
the Backend.

Change-Id: I08d3f4a384353b879ea90e1331097f583131ee40
Resolves: #31959
Releases: 4.7, 4.6, 4,5
Reviewed-on: http://review.typo3.org/6774
Reviewed-by: Markus Klein
Tested-by: Markus Klein
Reviewed-by: Steffen Ritter
Tested-by: Steffen Ritter