ash: [SHELL] Move flushall to the point just before _exit

ash: [SHELL] Move flushall to the point just before _exit

Upstream commit:

    We need to flush at the very end in case we've generated any errors
    before that.  The flushall call cannot perform a longjmp so it's
    safe there.

    Date: Sat, 22 Sep 2007 20:50:21 +0800
    [SHELL] Move flushall to the point just before _exit

    We need to flush at the very end in case we've generated any errors
    before that.  The flushall call cannot perform a longjmp so it's
    safe there.

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>