pkg/log: fix ineffassign issues

pkg/log/file_test.go

@@ -32,7 +32,9 @@ func TestLogFile(t *testing.T) {
 
 		Convey("Logging should add lines", func() {
 			err := fileLogWrite.WriteLine("test1\n")
+			So(err, ShouldBeNil)
 			err = fileLogWrite.WriteLine("test2\n")
+			So(err, ShouldBeNil)
 			err = fileLogWrite.WriteLine("test3\n")
 			So(err, ShouldBeNil)
 			So(fileLogWrite.maxlines_curlines, ShouldEqual, 3)