fix(manager): changed the column name the get_cluster searches for
fix(manager): changed the column name the get_cluster searches for

Due to changes in manager 2.0.2, the name of the column that houses
the cluster id's in the output of the 'sctool cluster list' command
changed from 'ID' to 'cluster id'.
In order to support all versions of manager 2.0.X, I've modified the
get_cluster function to support both column names, or in other words,
all 2.0.X manager versions.

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