allow non-loggedin users to access public bucket (#5570)

* conditionally render main action buttons

- Make bucket action will be available only for loggedIn users
- File upload button will be avaialble for loggedIn users
  and non-loggedIn users if the prefix is writable

* select the bucket and prefix from the url

When the url contains bucket and prefix, it will be selected
by default instead of the first bucket from the list.

* show BucketSearch only for LoggedIn users

* allow non-LoggedIn users to access public bucket

* removed unused Router imports

* fix test case failures in BucketList.test.js

* remove dupicate minioBrowserPrefix from url

since history is already initialized with minioBrowserPrefix,
no need to use it in push or replace

* remove unused match from App component

* remove unused minioBrowserPrefix imports

browser/app/js/objects/__tests__/reducer.test.js

@@ -27,6 +27,7 @@ describe("objects reducer", () => {
       currentPrefix: "",
       marker: "",
       isTruncated: false,
+      prefixWritable: false,
       shareObject: {
         show: false,
         object: "",
@@ -123,6 +124,14 @@ describe("objects reducer", () => {
     expect(newState.isTruncated).toBeFalsy()
   })
 
+  it("should handle SET_PREFIX_WRITABLE", () => {
+    const newState = reducer(undefined, {
+      type: actions.SET_PREFIX_WRITABLE,
+      prefixWritable: true
+    })
+    expect(newState.prefixWritable).toBeTruthy()
+  })
+
   it("should handle SET_SHARE_OBJECT", () => {
     const newState = reducer(undefined, {
       type: actions.SET_SHARE_OBJECT,