vecsum2: support non-SCR, improve time printf
vecsum2: support non-SCR, improve time printf

* s/VECSUM_SCR/VECSUM_LIBHDFS, since we don't know if SCR is being used.
* add hdfsReadFully to handle short reads (needed for non-SCR)
* Use .5g not .4g in time printfs

Signed-off-by: Colin Patrick McCabe <3142ce8a0bdba4a38073365893e6b74f72d9c512@cloudera.com>

umbrant/caching_benchmarking,umbrant/caching_benchmarking,umbrant/caching_benchmarking,umbrant/caching_benchmarking