[BUGFIX|PASQAL] Add return case when acquire step fails

[badtst]

Description of Change

In case the acquire of the qrmi resource failed within the SPANK plugin, _acquire_qpu would not return with a NULL pointer and error was not handled correctly by calling funtion slurm_spank_init_post_opt

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[CLAassistant]

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[ohtanim]

Good catch. Thanks,

[awennersteen]

Thanks!