Fix submodule initialization for CIMpp in Dockerfiles. #2579

Job	Run time
Scan Sourcecode with Cppcheck	3m 35s
Build dpsimpy and tests examples on Fedora Linux	7m 7s
Build Cxx examples on Fedora Linux	11m 40s
Run pytest over all notebooks	13m 42s
Execute WSCC 9 bus example	1m 21s
Run dpsim-mqtt-import-export VILLASnode example / Run a VILLASnode example across multiple containers	1m 30s
Run dpsim-mqtt VILLASnode example / Run a VILLASnode example across multiple containers	1m 37s
Run dpsim-mqtt-import-export-MIMO VILLASnode example / Run a VILLASnode example across multiple containers	1m 16s
Run dpsim-file VILLASnode example / Run a VILLASnode example across multiple containers	1m 25s
Run mqtt-cigre-mv-pf-profiles VILLASnode example / Run a VILLASnode example across multiple containers	1m 45s
Compare Notebook results	0s
	44m 58s

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