Werk #7700: mk_postgres: Fixed several problems

Originally the version of the client tools was taken, but what really matters is the version of the server. Terminate the script, if the server can not be queried.

In postgresql 9.2 the column state was introduced, which has to be queried to find the state of the sessions. The column state can be NULL.

Here the order of the columns did not match with what the server side expects, with the result, that there was never any active connection shown in the web-gui.

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