Revert of Comment out applying patchset dependencies in apply_issue.py (patchset #2 id:20001 of https://codereview.chromium.org/1194063003/)

Reason for revert:
https://chromereviews.googleplex.com/221697013/ has landed. Re-enable applying patchset dependencies in apply_issue.py

Original issue's description:
> Comment out applying patchset dependencies in apply_issue.py
> 
> Context is in the internal chrome-infra thread here:
> https://groups.google.com/a/google.com/d/msg/chrome-infra/dNQGjNoP-Dg/XDymPAwOCXkJ
> 
> NOPRESUBMIT=true
> 
> BUG=chromium:480453
> 
> Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=295800

TBR=phajdan.jr@chromium.org
BUG=chromium:480453

Review URL: https://codereview.chromium.org/1237703004

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@296016 0039d316-1c4b-4281-b951-d872f2087c98