exit with 127 if appled name wasn't found - it's more POSIXy

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
iproute: support onelink route option and print route flags

function                                             old     new   delta
print_route                                         1797    1865     +68
do_iproute                                          2097    2112     +15
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(add/remove: 0/0 grow/shrink: 2/0 up/down: 83/0)               Total: 83 bytes

Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>