sdcm/cluster: always compress the coredump file
sdcm/cluster: always compress the coredump file

Right now if the coredump is less than 5G, we will upload it directly
without compressing. This patch removed the size checking before spliting
and compressing. Then coredump will be compressed all the time, then
try to split if it's bigger than 5G.

Fixes issue #270

Signed-off-by: Amos Kong <eb01d8f828a6c9a20be4534e72e049aaf41503df@scylladb.com>

amoskong/scylla-cluster-tests,scylladb/scylla-cluster-tests,amoskong/scylla-cluster-tests,scylladb/scylla-cluster-tests,amoskong/scylla-cluster-tests,scylladb/scylla-cluster-tests,scylladb/scylla-longevity-tests,amoskong/scylla-cluster-tests,scylladb/scylla-cluster-tests,scylladb/scylla-longevity-tests,scylladb/scylla-cluster-tests,amoskong/scylla-cluster-tests,scylladb/scylla-longevity-tests