Fix the warning when you pass -c to step/next/si/ni.

During some cleanup the test for whether the thread plan
accepted an iteration count was reversed, so we give a 
warning when it will actually work, and don't when it won't.

<rdar://problem/32379280>

llvm-svn: 303832
diff --git a/lldb/source/Commands/CommandObjectThread.cpp b/lldb/source/Commands/CommandObjectThread.cpp
index 6b0f1b4..b585ef9 100644
--- a/lldb/source/Commands/CommandObjectThread.cpp
+++ b/lldb/source/Commands/CommandObjectThread.cpp
@@ -649,7 +649,7 @@
       new_plan_sp->SetOkayToDiscard(false);
 
       if (m_options.m_step_count > 1) {
-        if (new_plan_sp->SetIterationCount(m_options.m_step_count)) {
+        if (!new_plan_sp->SetIterationCount(m_options.m_step_count)) {
           result.AppendWarning(
               "step operation does not support iteration count.");
         }