Added missing StandardConversionSequence initialization

This is the second msan failure where UserDefinedConversion does not initialize
its `Before` member as identity conversion.

llvm-svn: 199997

clang/lib/Sema/SemaOverload.cpp

@@ -1134,6 +1134,7 @@ TryUserDefinedConversion(Sema &S, Expr *From, QualType ToType,
 
   if (UserDefResult == OR_Success) {
     ICS.setUserDefined();
+    ICS.UserDefined.Before.setAsIdentityConversion();
     // C++ [over.ics.user]p4:
     //   A conversion of an expression of class type to the same class
     //   type is given Exact Match rank, and a conversion of an