pox: set PWD to squelch bash's getcwd complaints
pox: set PWD to squelch bash's getcwd complaints

Since we run in a chroot, but our current directory isn't under the
chroot, bash complains a lot.  getcwd() fails every time it runs.

There are two errors that bash spits out

1) When the shell first starts, we get:

	shell-init: error retrieving current directory: getcwd: cannot
	access parent directories: No such file or directory

2) After every command, we get:

	job-working-directory: error retrieving current directory:
	getcwd: cannot access parent directories: No such file or
	directory

But by setting PWD, bash will not run getcwd after every command,
eliminating the second error message.  We still get the first message,
but I can live with that.

Signed-off-by: Barret Rhoden <66a4aaafefe344f5385586b74770760469cbac80@google.com>

GanShun/u-root,GanShun/u-root,hugelgupf/u-root,u-root/u-root,hugelgupf/u-root,GanShun/u-root,hugelgupf/u-root,u-root/u-root,u-root/u-root,hugelgupf/u-root