configure, zebra: Add some debug code to allow for fuzzing

configure, zebra: Add some debug code to allow for fuzzing

1) Write zserv api commands( one of each type ) to the side.  This will allow
us to use them as input for a fuzzer.

2) Add -c <file to pass to zapi read process> into zebra as a run-time
option of we've turned on fuzzing.

While in and of itself these are not terribly useful( you still need
an external fuzzer ), they provide an infrastructure to allow
tools like afl to test the zapi.

Signed-off-by: Donald Sharp <sharpd@cumulusnetworks.com>