blkreport, blkreset: small code clean ups

blkreport, blkreset: small code clean ups

Set variables read-only where possible.  Fix few code style issues, mostly
with spacing.  Avoid initializing variables if they are never read before
next update.  Remove "ERR: %d -> %s" message that repeated system error
three times, twice in that message and once at end of main that is the only
of these three left in place.

Signed-off-by: Sami Kerola <kerolasa@iki.fi>