whitespace
validate instrument data bam_path has size

This might be overreaching on the base Genome::Model::Build class but
it's definitely needed for anything that does BWA, BWAMEM, or BWASW
alignment.  For those types of alignment instrument data with a bam_path
but no size results in an invalid Workflow model that cannot be commited
to the DB.
InstrumentData needs an allocation to be valid
builds validate instrument data bam_path has size