Fix signature v2 handling for resource names (#4965)

Previously we were wrongly adding `?` as part
of the resource name, add a test case to check
if this is handled properly.

Thanks to @kannappanr for reproducing this.

Without this change presigned URL generated with following
command would fail with signature mismatch.
```
aws s3 presign s3://testbucket/functional-tests.sh
```

cmd/signature-v2_test.go

@@ -105,13 +105,18 @@ func TestDoesPresignedV2SignatureMatch(t *testing.T) {
 			},
 			expected: ErrSignatureDoesNotMatch,
 		},
-		// (6) Should error when the signature does not match.
+		// (6) Should not error signature matches with extra query params.
 		{
 			queryParams: map[string]string{
 				"response-content-disposition": "attachment; filename=\"4K%2d4M.txt\"",
 			},
 			expected: ErrNone,
 		},
+		// (7) Should not error signature matches with no special query params.
+		{
+			queryParams: map[string]string{},
+			expected:    ErrNone,
+		},
 	}
 
 	// Run each test case individually.