Make nodetool import congruent with the documentation by not relying on the folder structure of the imported SSTable files

nodetool import requires keyspace and table on the command line to import SSTables to. This
was not always working as specifying keypace and table while having SSTables located in the
directory structure which differed on keyspace and table (dir and parent dir) just
ignored them.

patch by Stefan Miklosovic; reviewed by Brandon Williams for CASSANDRA-19401
4 files changed