Disable leak checking for mksh; it's way too leaky.

When each shell leaks ~240 allocations, you can't see the leaks from
the program you ran with "adb shell".

Bug: 7291287
Change-Id: Ib8780db72ba0114ebdb24768537da74bbb61f354

Conflicts:
	libc/bionic/malloc_debug_common.cpp

Signed-off-by: Paul Beeler <sparksco@gmail.com>
Don't free anything when reporting leaks.

We don't know that they're not going to be cleaned up by a
C++ global destructor that runs after us. This is the case with
bootanimation, for example.

Bug: 7291287
Change-Id: Iba402514d1735fdc2ae4bc95b65396d816be46c0

Conflicts:
	libc/bionic/malloc_debug_check.cpp

Signed-off-by: Paul Beeler <sparksco@gmail.com>