Fix explicit interface impl of event

Author: jaredpar

src/Microsoft.DotNet.CodeFormatting.Tests/Rules/ExplicitVisibilityRuleTests.cs

@@ -120,6 +120,7 @@ interface I1
 {
     int Prop { get; set; }
     void M();
+    event EventHandler E;
 }
 
 class C : I1
@@ -130,6 +131,8 @@ int I1.Prop
         set { }
     }
     void I1.M() { } 
+    event EventHandler I1.E;
+    void M() { }
 }
 ";
 
@@ -138,6 +141,7 @@ internal interface I1
 {
     int Prop { get; set; }
     void M();
+    event EventHandler E;
 }
 
 internal class C : I1
@@ -148,6 +152,8 @@ int I1.Prop
         set { }
     }
     void I1.M() { } 
+    event EventHandler I1.E;
+    private void M() { }
 }
 ";
 

src/Microsoft.DotNet.CodeFormatting/Rules/ExplicitVisibilityRule.cs

@@ -80,6 +80,11 @@ public override SyntaxNode VisitPropertyDeclaration(PropertyDeclarationSyntax no
 
             public override SyntaxNode VisitEventDeclaration(EventDeclarationSyntax node)
             {
+                if (node.ExplicitInterfaceSpecifier != null)
+                {
+                    return node;
+                }
+
                 return EnsureVisibility(node, node.Modifiers, (x, l) => x.WithModifiers(l), SyntaxKind.PrivateKeyword);
             }