libbb: move common code into run_applet_and_exit

libbb: move common code into run_applet_and_exit

Both calls to run_applet_and_exit are followed by the same code
to print an error message and return status 127.  Remove this
duplication and make run_applet_and_exit static.

function                                             old     new   delta
run_applet_and_exit                                  675     667      -8
main                                                 119      92     -27
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 0/2 up/down: 0/-35)             Total: -35 bytes

Signed-off-by: Ron Yorston <rmy@pobox.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>