Removing trailing dot in path that samba doesn't seem to like

Fixes #5778
Added unit test for getId() and constructUrl()

Backport of f66ec8a02271e73755cb965107eca60f027ffe78
Fixed SMB file deletion success detection

Since unlink() smb4php doesn't return true on deletion success, we need
to check whether the file was deleted to confirm success.

Fixes #5866

Backport of eefd91355d54b7e49dd328cef9a9561ee51b0194
Merge pull request #5893 from owncloud/stable5-extstorage-smbfixes

[stable5] External storage SMB fixes for stat and unlink backport