Restarting service fails because database already connected

Comes back as SQAPL error, but should be checked and not cause error to be signalled

Modify `SQL.Connect` function:

```apl
      :If 0≠⊃r←SQA.Connect db,⍥⊆datasource
          :If 10009=2⊃r
              ⎕←'Already connected to ',⊃datasource
          :Else
              ⎕←r
              ('Could not connect to ',⊃datasource)⎕SIGNAL⊃r
          :EndIf
      :EndIf
```