Data sharing should be disabled in LatencyTest benchmark without --data_sharing flag

[JakubSosnovec]

When no XML profile is passed to the LatencyTest benchmark, data sharing policy is set to automatic by default. This will mean that data sharing is enabled regardless whether the --data_sharing command line flag is passed to the program or not.

Expected Behavior

Data sharing policy should be disabled when --data_sharing command line flag is not passed.

Current Behavior

Data sharing policy is automatic (and thus enabled) even if --data_sharing command line flag is not passed.

Steps to Reproduce

1. Run LatencyTest publisher and subscriber on the same device (to benchmark shared memory transport).
2. Try with passing --data_sharing flag.
3. Try without passsing --data_sharing flag.
4. Observe that the performance results are the same.

Suggested fix

Explicitly set the DataSharingQosPolicy to "off" whenever the command line flag is not passed in. Could be done here: https://github.com/eProsima/Fast-DDS/blob/master/test/performance/latency/LatencyTestPublisher.cpp#L274 and https://github.com/eProsima/Fast-DDS/blob/master/test/performance/latency/LatencyTestSubscriber.cpp#L226

[MiguelCompany]

@JakubSosnovec Would you mind doing the changes yourself and submitting a PR?