[FrameworkBundle] avoids cache:clear to break if new/old folders already exist
merged branch jfsimon/issue-6502 (PR #7260)

This PR was squashed before being merged into the 2.1 branch (closes #7260).

Commits
-------

1d3da29 [FrameworkBundle] avoids cache:clear to break if new/old folders already exist

Discussion
----------

[FrameworkBundle] avoids cache:clear to break if new/old folders already exist

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #6502

---------------------------------------------------------------------------

by mahmouds at 2013-03-04T19:07:20Z

:+1: