build: Skip initialization of Guacamole if not needed

[MoritzWeber0]

The Initialization raised several errors when the corresponding tables did already exist. We ignored those errors, but they are confusing for administrators.

Therefore, skip initialization if already done.

[sonarcloud[bot]]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 80.64%. Comparing base (bef9037) to head (8149673).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #1636 +/- ## ======================================= Coverage 80.64% 80.64% ======================================= Files 185 185 Lines 6090 6090 Branches 678 678 ======================================= Hits 4911 4911 Misses 1030 1030 Partials 149 149 ```

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