Need reviewer for 6917021: (file) copyTo/moveTo can overrwrite existing file when target associated with custom provider

[Alan Bateman]

When the copyTo/moveTo methods are invoked with a target that is 
associated with a custom file system then a simple copy/move 
implementation is used rather than the implementation for the platform. 
Thomas Salter pointed out a bug in this code whereby it could override a 
target file even when the REPLACE_EXISTING option is not used. The bug 
highlights that the current copy/move tests don't exercise the foreign 
provider case. The patch proposed extends the existing test for this 
case. In addition to the issue that Thomas ran into, the tests exposed 
two minor issues where the wrong exception is thrown.

The webrev with the changes is here:
  http://cr.openjdk.java.net/~alanb/6917021/webrev/

Thanks,
Alan.