examples/exception_path: fix out-of-bounds read

examples/exception_path: fix out-of-bounds read

When printing out stats from the exception_path app, all possible
lcore_ids are iterated. However, the app only supports up to 64 cores.
To prevent possible errors, and to remove coverity warnings,
explicitly check for out-of-range lcore ids before printing.

Coverity issue: 268335
Fixes: af75078fece3 ("first public release")
Cc: stable@dpdk.org
Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>