DSL2: bamqc does not get stats across all references in multi-ref cases

[ilight1542]

Description of the bug

Multiqc fails to display mapping statistics across multiple reference genomes, instead only displaying a single sample-reference pair (anonymous to which reference) on multiple metrics eg Coverage Histogram and Cumulative genome coverage plots, and in summary table

Steps to reproduce

Steps to reproduce the behaviour:

git checkout dev

nextflow run main.nf -profile test_microbial,singularity -w ./work --outdir ./out_test_microbial

Expected behaviour

Ref-by-sample descriptions for bamqc outputs