Check if external storage dir already exists to fix #128

- Check if external storage dir already exists when trying to create it
- Get rid of erroneous warning message in said case
- Remove autoboxing of boolean value
- Add test case to verify external storage dir creation works

hockeysdk/src/androidTest/java/net/hockeyapp/android/EnvironmentTest.java

@@ -0,0 +1,31 @@
+package net.hockeyapp.android;
+
+import android.support.test.runner.AndroidJUnit4;
+
+import junit.framework.TestCase;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+
+import java.io.File;
+
+/**
+ * <h3>Description</h3>
+ *
+ * This class provides testing for the environment features, such as the SDK wide constants.
+ */
+@RunWith(AndroidJUnit4.class)
+public class EnvironmentTest extends TestCase {
+
+    /**
+     * Test to verify basic creation of the external storage directory works.
+     */
+    @Test
+    public void basicStorageDirTest() {
+        File storageDir = Constants.getHockeyAppStorageDir();
+
+        assertNotNull(storageDir);
+        assertTrue(storageDir.exists());
+    }
+
+}

hockeysdk/src/main/java/net/hockeyapp/android/Constants.java

@@ -131,7 +131,7 @@ public static File getHockeyAppStorageDir() {
         File externalStorage = Environment.getExternalStorageDirectory();
 
         File dir = new File(externalStorage.getAbsolutePath() + "/" + Constants.FILES_DIRECTORY_NAME);
-        Boolean success = dir.mkdirs();
+        boolean success = dir.exists() || dir.mkdirs();
         if (!success) {
             HockeyLog.warn("Couldn't create HockeyApp Storage dir");
         }