tests: blacklist failing test on arduino-mega2560

.travis.yml

examples/ccn-lite-client/Makefile

examples/ccn-lite-relay/Makefile

examples/riot_and_cpp/Makefile

examples/rpl_udp/Makefile

sys/pipe/pipe_dynamic.c

tests/bloom/Makefile

tests/coap/Makefile

tests/libfixmath_unittests/Makefile

tests/net_if/Makefile

tests/pnet/Makefile

tests/posix_sleep/Makefile

tests/pthread/Makefile

tests/pthread_barrier/Makefile

tests/pthread_cleanup/Makefile

tests/pthread_condition_variable/Makefile

tests/pthread_cooperation/Makefile

tests/pthread_rwlock/Makefile

tests/vtimer_msg_diff/Makefile