Use xcalloc() instead of xmalloc() with an inline multiplication.

src/common/assoc_mgr.c

src/common/gres.c

src/common/job_resources.c

src/common/node_select.c

src/common/parse_config.c

src/common/read_config.c

src/common/slurm_acct_gather_energy.c

src/common/slurm_cred.c

src/common/slurm_jobacct_gather.c

src/common/slurm_protocol_api.c

src/common/slurm_protocol_pack.c

src/common/slurm_step_layout.c

src/common/switch.c

src/plugins/burst_buffer/cray/burst_buffer_cray.c

src/plugins/checkpoint/blcr/checkpoint_blcr.c

src/plugins/priority/multifactor/priority_multifactor.c

src/plugins/select/cons_res/select_cons_res.c

src/plugins/select/cons_tres/select_cons_tres.c

src/plugins/select/cray/select_cray.c

src/plugins/select/linear/select_linear.c