Handle default kernel cmdline if multiple boot entries for the default kernel are defined #4128

Job	Run time
Run unit tests in containers (Run unit tests for el9toel10 and common repositories on python 3.12...	1m 42s
Run unit tests in containers (Run python linters for el9toel10 and common repositories on python ...	1m 29s
Run unit tests in containers (Run unit tests for el9toel10 and common repositories on python 3.9,...	47s
Run unit tests in containers (Run python linters for el9toel10 and common repositories on python ...	1m 14s
Run unit tests in containers (Run unit tests for el8toel9 and common repositories on python 3.9, ...	1m 19s
Run unit tests in containers (Run python linters for el8toel9 and common repositories on python 3...	1m 50s
Run unit tests in containers (Run unit tests for el8toel9 and common repositories on python 3.6, ...	1m 5s
Run unit tests in containers (Run python linters for el8toel9 and common repositories on python 3...	3m 22s
Run unit tests in containers (Run unit tests for el7toel8 and common repositories on python 3.6, ...	1m 26s
Run unit tests in containers (Run python linters for el7toel8 and common repositories on python 3...	4m 25s
Run unit tests in containers (Run unit tests for el7toel8 and common repositories on python 2.7, ...	1m 18s
Run unit tests in containers (Run python linters for el7toel8 and common repositories on python 2...	5m 28s
	25m 25s

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