libmultipath: Do not use 'sscanf' for parsing integers

'sscanf' doesn't really have a way of signalling errors,
so strtoul(l) should be used instead.

References: bnc#889927

Signed-off-by: Hannes Reinecke <hare@suse.de>
libmultipath: finally fix dev_loss_tmo setting

A 'no_path_retry' setting of '0' (or 'fail') and a
non-zero fast_io_fail_tmo setting would cause the
dev_loss_tmo setting to become '0'.
As this was an invalid value the lpfc driver would
silently modify it to '1'.

References: bnc#889927

Signed-off-by: Hannes Reinecke <hare@suse.de>