change fractional cpu specifications to round to nearest integer rather than truncate

[sorelfitzgibbon]

When converting json specified cpu_fraction to the number of cpus to be used for the process on a specific node, round to the nearest integer. Currently 1.99 would become 1 cpu. call-sSNV resource specifications have been set assuming, per conversation with @yashpatel6, this will be implemented, although it's currently only relevant to the default set.