removed APC on the CLI for Travis as it does not work well with PHPUnit and Composer anyway
Revert PHPUnit version, revert APC configuration
minor #10623 [2.3] Fix travis build (fabpot, romainneutron)

This PR was merged into the 2.3 branch.

Discussion
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[2.3] Fix travis build

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | n/a
| License       | MIT

This PR replaces #10595 and fixes travis build on branch 2.3

Commits
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f613caa Revert PHPUnit version, revert APC configuration
9bdd3d1 removed APC on the CLI for Travis as it does not work well with PHPUnit and Composer anyway