SetDebug methods are maintained for compatibility.

This is part of a patch series to process the INIT opcode on
mount. This will enable filesystems to switch functionality depending
on kernel settings.

In order to get the debug output for the INIT opcode, the debug option
must be passed to the mount method.

Deprecate the SetDebug methods. There is often little practical use in
toggling debug on the fly, since the error scenarios depend on timing
details, and must usually be isolated into unittests.

Change-Id: I221c995add5f7621b627f738d7e97af7daf81b2a