Warn user when scb is provided but there is no file

[sahankj2000]

Description

When a user provides the secureconnectbundle to a cqld4 adapter, it silently fails in the driver without telling the user it could not find the file

Issues: 1668 and 982

Original Error:

java.lang.RuntimeException: javax.script.ScriptException: io.nosqlbench.nb.api.errors.OpConfigError: Error while configuring op from workload template: 
[from:yaml:/path/to/workload.yaml]  cause: AllNodesFailedException:Could not reach any contact point, 
make sure you've provided valid addresses (showing first 1 nodes, use getAllErrors() for more): 
Node(endPoint=localhost/127.0.0.1:9042, hostId=null, hashCode=31dd7ba2): 
...

After adding warning:

4047 ERROR [main] Cqld4Space   Unable to load path /path/to/non-existing/bundle.zip
4059 ERROR [main] NBInvokableCommand error in command (stack trace follows): NBScriptedCommand 
{container="default",instance="default",jobname="nosqlbench",node="192.168.0.179",session="nOjgBos",step="phase_1"}: 
java.lang.RuntimeException: javax.script.ScriptException: io.nosqlbench.nb.api.errors.OpConfigError: Error while configuring 
op from workload template: [from:yaml:/path/to/workload.yaml]  cause: RuntimeException:Unable to load path 
/path/to/non-existing/bundle.zip Unable to load path /path/to/non-existing/bundle.zip
...

[sumit-ct]

Should we add else case when scb file itself is not given? Or is it handled someplace else, in that case do we need to remove first if condition?