Bug 578841: Fix unknown trace opening with FTrace

No longer pass a negative confidence value from TrimmedFtraceTrace,
while validating if the trace to open is an FTrace or not. This led to
an IllegalArgumentException from TraceValidationStatus that was failing
the opening of a non-FTrace file.

Confidence towards being an FTrace is zero (0) for this specific case,
so this fixed line of code passed a negative confidence value prior. A
complete affected use case description (with steps) is in Bug 578841.

This fix depends on [1]'s own NumberFormatException fix.

[1] https://git.eclipse.org/r/c/tracecompass.incubator/org.eclipse.tracecompass.incubator/+/190837

Change-Id: I8546cf870ca088f1176685df292b334dec86fe04
Signed-off-by: Marco Miller <marco.miller@ericsson.com>
Reviewed-on: https://git.eclipse.org/r/c/tracecompass.incubator/org.eclipse.tracecompass.incubator/+/190968
Tested-by: Trace Compass Bot <tracecompass-bot@eclipse.org>
Tested-by: Matthew Khouzam <matthew.khouzam@ericsson.com>
Reviewed-by: Matthew Khouzam <matthew.khouzam@ericsson.com>

tracetypes/org.eclipse.tracecompass.incubator.ftrace.core/src/org/eclipse/tracecompass/incubator/internal/ftrace/core/trace/TrimmedFtraceTrace.java

@@ -31,7 +31,8 @@ public IStatus validate(IProject project, String path) {
         IStatus status = super.validate(project, path);
         if (status instanceof TraceValidationStatus) {
             TraceValidationStatus traceValidationStatus = (TraceValidationStatus) status;
-            status = new TraceValidationStatus(traceValidationStatus.getConfidence() - 1, traceValidationStatus.getPlugin());
+            int trimmedConfidence = Math.max(0, traceValidationStatus.getConfidence() - 1);
+            status = new TraceValidationStatus(trimmedConfidence, traceValidationStatus.getPlugin());
         }
         return status;
     }