[libcheckers] workaround for rather profound path checking issue

[libcheckers] workaround for rather profound path checking issue

Overloaded storage response time can be very long.
SG_IO timouts after DEF_TIMEOUT milliseconds, and checkers interprets this
as a path failure. multipathd then proactively evicts the path from the DM
multipath table in this case.

This generaly snow balls and ends up in full eviction and IO errors for end
users. Bad. This may also cause SCSI bus resets, causing disruption for all
local and external storage hardware users.

Provision a long timeout. Longer than any real-world application would cope
with.

If someone can suggest a real fix, like an evidence the ioctl timed out,
voice up. The ioctl being blocking, I'd rather lower the timeout and retry
than apply this workaround.