Try to fix race in getExistentialMetadata() unit tests

(cherry picked from commit a836009)

Author: slavapestov

unittests/runtime/Metadata.cpp

@@ -443,16 +443,19 @@ TEST(MetadataTest, getExistentialMetadata) {
     });
 
   // protocol compositions are order-invariant
-  const ProtocolDescriptor *protoList4[] = {
-    &ProtocolA,
-    &ProtocolB
-  };
-  const ProtocolDescriptor *protoList5[] = {
-    &ProtocolB,
-    &ProtocolA
-  };
   RaceTest_ExpectEqual<const ExistentialTypeMetadata *>(
     [&]() -> const ExistentialTypeMetadata * {
+
+      const ProtocolDescriptor *protoList4[] = {
+        &ProtocolA,
+        &ProtocolB
+      };
+
+      const ProtocolDescriptor *protoList5[] = {
+        &ProtocolB,
+        &ProtocolA
+      };
+
       auto ab = swift_getExistentialTypeMetadata(ProtocolClassConstraint::Any,
                                                 /*superclass=*/nullptr,
                                                 2, protoList4);
@@ -514,13 +517,14 @@ TEST(MetadataTest, getExistentialMetadata) {
       return noWitnessTable;
     });
 
-  const ProtocolDescriptor *protoList8[] = {
-    &ProtocolNoWitnessTable,
-    &ProtocolA,
-    &ProtocolB
-  };
   RaceTest_ExpectEqual<const ExistentialTypeMetadata *>(
     [&]() -> const ExistentialTypeMetadata * {
+      const ProtocolDescriptor *protoList8[] = {
+        &ProtocolNoWitnessTable,
+        &ProtocolA,
+        &ProtocolB
+      };
+
       auto mixedWitnessTable
         = swift_getExistentialTypeMetadata(ProtocolClassConstraint::Class,
                                            /*superclass=*/nullptr,
@@ -560,12 +564,13 @@ TEST(MetadataTest, getExistentialMetadata) {
       return special;
     });
 
-  const ProtocolDescriptor *protoList10[] = {
-    &ProtocolError,
-    &ProtocolA
-  };
   RaceTest_ExpectEqual<const ExistentialTypeMetadata *>(
     [&]() -> const ExistentialTypeMetadata * {
+      const ProtocolDescriptor *protoList10[] = {
+        &ProtocolError,
+        &ProtocolA
+      };
+
       auto special
         = swift_getExistentialTypeMetadata(ProtocolClassConstraint::Any,
                                            /*superclass=*/nullptr,