Unimplement Console.readPassword and remove test

ConsoleTest.test_readPassword* fails CTS tests.

Context: Under standard Android applications the
System.console() method will return null.

The Console.readPassword() method must turn off echo.

Under automated tests the ConsoleTest is exercising
a Console object with fake stdout / stdin streams to
get around the absence of a System.console().

setEcho() is hardcoded to use stdin / stdout in
the native code. Under the test runners stdin / stdout
are not connected to a TTY leading to a ENOTTY.

Under Android readPassword is unimportant. Rather than leaving
untested security-related code the password methods are being
unimplemented. It is unlikely this code has ever been used on
Android given the absence of a System Console instance.

Bug: 12491103
Change-Id: I755c014e6b53236f5bef0535be137dd721918b44