Speed up running the tests of the IO module from Maven

The `mvn test` command, when run in the IO module, now takes 15 seconds instead of 5 minutes.
This has been achieved by moving many of the tests to the verification phase instead of the test phase, by running them with the failsafe plugin instead of surefire.
Also, the tests are now executed in parallel.

community/io/pom.xml

@@ -120,6 +120,13 @@ the relevant Commercial Agreement.
           </jvmArgs>
         </configuration>
       </plugin>
+      <plugin>
+        <artifactId>maven-surefire-plugin</artifactId>
+        <configuration>
+          <parallel>methods</parallel>
+          <perCoreThreadCount>2</perCoreThreadCount>
+        </configuration>
+      </plugin>
     </plugins>
   </build>
 

community/io/src/main/java/org/neo4j/io/fs/DefaultFileSystemAbstraction.java

@@ -94,14 +94,14 @@ public boolean mkdir( File fileName )
     @Override
     public void mkdirs( File path ) throws IOException
     {
-        if (path.exists())
+        if ( path.exists() )
         {
             return;
         }
 
-        boolean directoriesWereCreated = path.mkdirs();
+        path.mkdirs();
 
-        if (directoriesWereCreated)
+        if ( path.exists() )
         {
             return;
         }

community/io/src/test/java/org/neo4j/io/fs/FileSystemAbstractionInterruptionTest.java

@@ -84,20 +84,16 @@ public FileSystemAbstractionInterruptionTest( @SuppressWarnings( "UnusedParamete
         fs = factory.newInstance();
     }
 
-    @Before
-    public void interruptPriorToCall()
-    {
-        Thread.currentThread().interrupt();
-    }
-
     @Before
     public void createWorkingDirectoryAndTestFile() throws IOException
     {
+        Thread.interrupted();
         fs.mkdirs( testdir.directory() );
         file = testdir.file( "a" );
         fs.create( file ).close();
         channel = null;
         channelShouldBeClosed = false;
+        Thread.currentThread().interrupt();
     }
 
     private StoreChannel channel;