Only throw error if dir does not exist after attempting to create

Fixes #15

Author: steffenkleinle

android/src/main/java/com/ReactNativeBlobUtil/ReactNativeBlobUtilFS.java

@@ -57,7 +57,7 @@ static void writeFile(String path, String encoding, String data, final boolean a
 
             if (!f.exists()) {
                 if (dir != null && !dir.exists()) {
-                    if (!dir.mkdirs()) {
+                    if (!dir.mkdirs() && !dir.exists()) {
                         promise.reject("EUNSPECIFIED", "Failed to create parent directory of '" + path + "'");
                         return;
                     }
@@ -129,7 +129,7 @@ static void writeFile(String path, ReadableArray data, final boolean append, fin
 
             if (!f.exists()) {
                 if (dir != null && !dir.exists()) {
-                    if (!dir.mkdirs()) {
+                    if (!dir.mkdirs() && !dir.exists()) {
                         promise.reject("ENOTDIR", "Failed to create parent directory of '" + path + "'");
                         return;
                     }
@@ -445,7 +445,7 @@ void writeStream(String path, String encoding, boolean append, Callback callback
 
             if (!dest.exists()) {
                 if (dir != null && !dir.exists()) {
-                    if (!dir.mkdirs()) {
+                    if (!dir.mkdirs() && !dir.exists()) {
                         callback.invoke("ENOTDIR", "Failed to create parent directory of '" + path + "'");
                         return;
                     }