smartplaylists: fix generated SQL query for multi-value rules with a negated parameter (fixes #15313)

This fixes the problem described in http://trac.xbmc.org/ticket/15313. When a user defines a smartplaylist rule with multiple values and uses a negated operator like "does not contain" or "does not equal" the resulting SQL query doesn't follow De Morgan's laws and produces something like
```
<field> does not contain <value1> or <field> does not contain <value2>
```
but it should be
```
<field> does not contain <value1> and <field> does not contain <value2>
```
i.e. it needs to use an "AND" operator instead of an "OR" operator.