checkpointing: fix bug from curTick accessor conversion.
checkpointing: fix bug from curTick accessor conversion.

Regex replacement of curTick with curTick() accidentally
changed checkpoint key string for serialization but not
for unserialization.

andrewfu0325/gem5-aladdin,andrewfu0325/gem5-aladdin,andrewfu0325/gem5-aladdin,andrewfu0325/gem5-aladdin,andrewfu0325/gem5-aladdin,andrewfu0325/gem5-aladdin,andrewfu0325/gem5-aladdin