When trying to upgrade from 7.0.0 to 7.0.2, the manual upgrade path
(e.g. ` sudo -u www-data /usr/bin/php5 ./occ upgrade`) exits with the
following fatal error:

```
/var/www/owncloud# php occ upgrade
PHP Fatal error:  Call to a member function
  disableQueryStatementCaching() on a non-object in
  /var/www/owncloud/lib/private/db.php on line 423
```

This is caused by the self::$connection static variable having not
been initialized at the point of call. Adding a self::connect() fixes
the issue.

See https://forum.owncloud.org/viewtopic.php?f=29&t=23398&p=68556#p68556

- re-enable encryption migration tests
- sqlite requires reconnect after schema changes

This reverts commit 73062040.

I use the term socket for any extension, either unix socket, or internet socket (port).

I check if the socket is all digits
* only integers 0 and larger would pass this test.
I then check if the string is less than or equal to the maximum port number.

By using "if($socket)" I make sure socket isn't false, empty, or the string '0'.

I don't believe I need to initialize $port because $port will always be set if $socket is true. Please show me if I am wrong here. Thanks

This passes anything that is not a valid port (0<int<65535) as a unix socket.
I tested this with unix sockets; this needs to be tested with a non-standard mysql port as well but I don't foresee any issues.

To use a unix socket, even one different than PHP's mysql.default_socket..
* Database Host = localhost:/path/to/socket

When upgrade, also simulate the database schema update for apps before
doing the actual upgrade.

- kill replaceDB() - this function is unused and it's implementation obviously wrong
- add method annotation OC_DB_StatementWrapper::fetchAll
- remove duplicate code in Test_DBSchema and reuse OC_DB::tableExists
- remove unused variables

* test case added to avoid adding them later

This patch was automatically generated as part of the following inspection:
https://scrutinizer-ci.com/g/owncloud/core/inspections/cdfecc4e-a37e-4233-8025-f0d7252a8720

Enabled analysis tools:
 - PHP Analyzer
 - JSHint
 - PHP Copy/Paste Detector
 - PHP PDepend

Conflicts:
	lib/private/vcategories.php