oeqa dump.py: add error counter and stop after 5 failures

oeqa dump.py: add error counter and stop after 5 failures

If test target qemu machine hangs completely, dump_target() calls
over serial console are taking a long time to time out, possibly
for every failing ssh command execution and a lot of test cases,
and same with dump_monitor().

Instead of trying for ever, count errors and after 5 stop trying
to dump_target() and dump_monitor() completely.

These help to end testing earlier when a test target is completely
deadlocked and all ssh, serial and QMP communication with it are
failing.

Signed-off-by: Mikko Rapeli <mikko.rapeli@linaro.org>
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
(cherry picked from commit d9ad0a055abba983c6cee1dca4d2f0a8a3c48782)
Signed-off-by: Steve Sakoman <steve@sakoman.com>