src/lib/hardware/vfio: get path to driver from environment variables
src/lib/hardware/vfio: get path to iommu_groups from environment variables
src/lib/hardware/vfio: function to check vfio availability
src/lib/hardware/pci: get path to pci devices from environment variables
src/lib/hardware/bus: use new functions to get path
src/apps/intel/intel_app: check vfio before test execution
src/apps/vhost/vhost_user: check vfio before test execution
src/apps/intel/intel_app: get pci id for test from environment variables
src/apps/vhost/vhost_user: get pci id for test from environment variables
src/core/memory: calculate size in bytes only if varialble is not null
src/core/memory: get path to hugepages files from environment variables
src/core/memory: get path to meminfo file from environment variable