Spades often gets stuck on read error correction

[bsiranosian]

This happens in about 5% of cases, looping away and wasting compute with no error. See ablab/spades#152

A solution is to split the read correction and assembler, and skip the read correction if it fails to compete after some reasonable amount of time.
spades-hammer can be run alone, then spades with the --only-assembler option