need initClause when catch Exception and throw new Exception in cli

through CASSANDRA-2746 , we added initCause to the Cli such that we could see more meaningful exception stacktrace when certain exception is thrown.

However, there are still some other area, eg:

executeGetWithConditions(Tree)
executeSet(Tree)
executeIncr(Tree, long)
etc etc...

basically any time you do a

            {
                throw new RuntimeException(e.getMessage());
            }

the real exception is lost. The right approach should be:

        catch (Exception e)
        {
            throw new RuntimeException(e.getMessage(), e);
        }

eg: i was getting this:
null
java.lang.RuntimeException
at org.apache.cassandra.cli.CliClient.executeCLIStatement(CliClient.java:310)
at org.apache.cassandra.cli.CliMain.processStatement(CliMain.java:217)
at org.apache.cassandra.cli.CliMain.main(CliMain.java:345)
Caused by: java.lang.RuntimeException
at org.apache.cassandra.cli.CliClient.executeGetWithConditions(CliClient.java:815)
at org.apache.cassandra.cli.CliClient.executeCLIStatement(CliClient.java:208)
... 2 more

but i have no idea what the problem is with just the above stack trace.

with the fix, this would tell us more:
null
java.lang.RuntimeException
at org.apache.cassandra.cli.CliClient.executeCLIStatement(CliClient.java:310)
at org.apache.cassandra.cli.CliMain.processStatement(CliMain.java:217)
at org.apache.cassandra.cli.CliMain.main(CliMain.java:345)
Caused by: java.lang.RuntimeException
at org.apache.cassandra.cli.CliClient.executeGetWithConditions(CliClient.java:815)
at org.apache.cassandra.cli.CliClient.executeCLIStatement(CliClient.java:208)
... 2 more
Caused by: UnavailableException()
at org.apache.cassandra.thrift.Cassandra$get_indexed_slices_result.read(Cassandra.java:14065)
at org.apache.cassandra.thrift.Cassandra$Client.recv_get_indexed_slices(Cassandra.java:810)
at org.apache.cassandra.thrift.Cassandra$Client.get_indexed_slices(Cassandra.java:782)
at org.apache.cassandra.cli.CliClient.executeGetWithConditions(CliClient.java:806)
... 3 more