[FIR] Union CFG edges from postponed lambdas only if outer call was analyzed independently

Before this change nodes unification was called if outer call was
  completed in the FULL mode, but it may happen even if this call is
  actually a part of some other outer call

compiler/testData/codegen/box/smartCasts/kt44814.dot

@@ -706,8 +706,9 @@ digraph kt44814_kt {
     191 -> {192};
     192 -> {193};
     193 -> {194};
-    194 -> {195};
     194 -> {182} [color=green style=dashed];
+    194 -> {195} [color=green];
+    194 -> {202} [style=dotted];
     195 -> {196};
     196 -> {197 201};
     197 -> {198};