Config: remove more test specific conditions

The `--cache` option could not be tested as the `Config` class did not allow for it to be set in a test situation.

This "conditional ignore" was introduced in commit 24c7a7f around the same time the caching feature was introduced.
The commit message doesn't give a reason for introducing the conditional ignore. I can only guess why and my guess would be that it was to prevent test runs being influence by dev-user specific system-wide defaults from a `CodeSniffer.conf` file.

In my opinion, that is not a good reason for keeping the "conditional ignore".
* First of all, the default setting is for the cache to be _off_, so by default, tests wouldn't use the cache anyhow.
* Second of all, the problem of interference from dev-user specific system-wide defaults was fixed by the introduction of the `ConfigDouble` and the `AbstractRealConfigTestCase`.

All in all, I think these conditions can be safely removed.

Do keep in mind though that subsequent test runs for tests involving caching may re-use the cache from an earlier run test.
To prevent that, set an explicit cacheFile for the test using `--cache=<filename>` and remove this cache file after running the test(s) via the `tearDown[AfterClass]()` method.

Note: one of the removed conditions also affected the `--parallel` option, but only for system-wide settings, not for CLI arguments.

Related to 966

Author: jrfnl

src/Config.php

@@ -650,16 +650,14 @@ public function restoreDefaults()
             $this->colors = (bool) $colors;
         }
 
-        if (defined('PHP_CODESNIFFER_IN_TESTS') === false) {
-            $cache = self::getConfigData('cache');
-            if ($cache !== null) {
-                $this->cache = (bool) $cache;
-            }
+        $cache = self::getConfigData('cache');
+        if ($cache !== null) {
+            $this->cache = (bool) $cache;
+        }
 
-            $parallel = self::getConfigData('parallel');
-            if ($parallel !== null) {
-                $this->parallel = max((int) $parallel, 1);
-            }
+        $parallel = self::getConfigData('parallel');
+        if ($parallel !== null) {
+            $this->parallel = max((int) $parallel, 1);
         }
 
     }//end restoreDefaults()
@@ -817,10 +815,8 @@ public function processLongArgument($arg, $pos)
                 break;
             }
 
-            if (defined('PHP_CODESNIFFER_IN_TESTS') === false) {
-                $this->cache = true;
-                $this->overriddenDefaults['cache'] = true;
-            }
+            $this->cache = true;
+            $this->overriddenDefaults['cache'] = true;
             break;
         case 'no-cache':
             if (isset($this->overriddenDefaults['cache']) === true) {
@@ -928,9 +924,7 @@ public function processLongArgument($arg, $pos)
 
                 $this->exclude = $this->parseSniffCodes(substr($arg, 8), 'exclude');
                 $this->overriddenDefaults['exclude'] = true;
-            } else if (defined('PHP_CODESNIFFER_IN_TESTS') === false
-                && substr($arg, 0, 6) === 'cache='
-            ) {
+            } else if (substr($arg, 0, 6) === 'cache=') {
                 if ((isset($this->overriddenDefaults['cache']) === true
                     && $this->cache === false)
                     || isset($this->overriddenDefaults['cacheFile']) === true