Fix PATH for crosh sub-shells to be more user-friendly
Fix PATH for crosh sub-shells to be more user-friendly

BUG=none
TEST=ctrl-alt-T to start crosh; invoke 'shell' command; echo $PATH; echo $SHELL

Review URL: http://codereview.chromium.org/3085002

joshfire/chromiumos-platform-window_manager,joshfire/chromiumos-platform-window_manager,joshfire/chromiumos-platform-window_manager,joshfire/chromiumos-platform-window_manager