storageproxyd: Fix inverted conditional in error checking

check_scci_sense (now renamed unexpected_scsi_sense) was supposed to
return false iff the sense data was valid and did not contain an error.
This return value was inverted. Invert the return values and rename the
function to clarify its role.

Test: m storageproxyd
Bug: 195544379
Change-Id: I3b84188aabe58345a83d2fd57bb8103e730cf365