The old password field is now preserved in the JSON structure to make
sure that the order is preserved.
This is a quick fix until the UI is fixed to not rely on the PHP array
key order.
- test config was written correctly (global and local)
- test that personal mount points can be added for allowed backends
- test that personal mount points cannot be added for disallowed backends
- added $skipTest flag to make it possible add mount points without
doing an actual check/connection (note: this is necessary because the
static class OC_Mount_Config cannot be mocked)