Fix handling of suppressed exception

On API 19 and 20, the library was trying to save "suppressed exceptions"
in the loader.dexElementsSuppressedExceptions but the field is not
there, it's in DexPathList, so the correct path is
loader.pathList.dexElementsSuppressedExceptions.

Bug: 28808797
Change-Id: I549e2120e744345a86df2f588f03823d9dfab659
diff --git a/library/src/android/support/multidex/MultiDex.java b/library/src/android/support/multidex/MultiDex.java
index 1e04c19..982bfbf 100644
--- a/library/src/android/support/multidex/MultiDex.java
+++ b/library/src/android/support/multidex/MultiDex.java
@@ -425,9 +425,9 @@
                     Log.w(TAG, "Exception in makeDexElement", e);
                 }
                 Field suppressedExceptionsField =
-                        findField(loader, "dexElementsSuppressedExceptions");
+                        findField(dexPathList, "dexElementsSuppressedExceptions");
                 IOException[] dexElementsSuppressedExceptions =
-                        (IOException[]) suppressedExceptionsField.get(loader);
+                        (IOException[]) suppressedExceptionsField.get(dexPathList);
 
                 if (dexElementsSuppressedExceptions == null) {
                     dexElementsSuppressedExceptions =
@@ -443,7 +443,7 @@
                     dexElementsSuppressedExceptions = combined;
                 }
 
-                suppressedExceptionsField.set(loader, dexElementsSuppressedExceptions);
+                suppressedExceptionsField.set(dexPathList, dexElementsSuppressedExceptions);
             }
         }