Fixed SMB file deletion success detection

Since unlink() smb4php doesn't return true on deletion success, we need
to check whether the file was deleted to confirm success.

Fixes #5866

apps/files_external/lib/smb.php

@@ -81,6 +81,18 @@ class SMB extends \OC\Files\Storage\StreamWrapper{
 		}
 	}
 
+	/**
+	 * Unlinks file
+	 * @param string @path
+	 */
+	public function unlink($path) {
+		unlink($this->constructUrl($path));
+		clearstatcache();
+		// smb4php still returns false even on success so
+		// check here whether file was really deleted
+		return !file_exists($path);
+	}
+
 	/**
 	 * check if a file or folder has been updated since $time
 	 * @param string $path

tests/lib/files/storage/storage.php

@@ -182,8 +182,9 @@ abstract class Storage extends \PHPUnit_Framework_TestCase {
 		$this->assertTrue($this->instance->hasUpdated('/lorem.txt', $ctimeStart - 5));
 		$this->assertTrue($this->instance->hasUpdated('/', $ctimeStart - 5));
 
-		$this->assertTrue(($ctimeStart - 5) <= $mTime);
-		$this->assertTrue($mTime <= ($ctimeEnd + 1));
+		// check that ($ctimeStart - 5) <= $mTime <= ($ctimeEnd + 1)
+		$this->assertGreaterThanOrEqual(($ctimeStart - 5), $mTime);
+		$this->assertLessThanOrEqual(($ctimeEnd + 1), $mTime);
 		$this->assertEquals(filesize($textFile), $this->instance->filesize('/lorem.txt'));
 
 		$stat = $this->instance->stat('/lorem.txt');
@@ -202,6 +203,17 @@ abstract class Storage extends \PHPUnit_Framework_TestCase {
 		$this->assertTrue($this->instance->hasUpdated('/', $mtimeStart - 5));
 	}
 
+	public function testUnlink() {
+		$textFile = \OC::$SERVERROOT . '/tests/data/lorem.txt';
+		$this->instance->file_put_contents('/lorem.txt', file_get_contents($textFile));
+
+		$this->assertTrue($this->instance->file_exists('/lorem.txt'));
+
+		$this->assertTrue($this->instance->unlink('/lorem.txt'));
+
+		$this->assertFalse($this->instance->file_exists('/lorem.txt'));
+	}
+
 	public function testFOpen() {
 		$textFile = \OC::$SERVERROOT . '/tests/data/lorem.txt';