Fix error when using lcd, amend commit 11c1ca1.

[farhanmustar]

Fix cd command used is not from cd variable when reverting back the working directory to original path.

[farhanmustar]

Hi @junegunn , after carefully debugging this issue i have finally realize the actual issue.
The issue is that the command to go back to prev directory (cd -) is actually running in the new tab.
This mean the window before running GV command is not changed to previous directory, instead our GV tab is changing to that directory. Somehow in windows this command does not throw any error but in ubuntu it is throwing error.

Therefore this is my final fix for the issue. But maybe can be refactor if dont like the idea of putting b:current_path directory.
Maybe changing to passing through function param instead.