Add support for autodetecting a MLNX HCA in the rmaps min distance feature. In this way, .ini files distributed with software stacks need not specify a particular HCA but instead may select the key word auto which will automatically select the discovered device. To use this feature, simply pass the keyword auto instead of a specific device name, --mca rmaps_base_dist_hca auto. If more than one card is installed, the mapper will inform the user of this and, at this point, the user will then need to specify which card via the normal route, e.g. --mca rmaps_base_dist_hca <dev_name>. This should be added to \ncmr=v1.7.4:reviewer=rhc:subject=Autodetect logic for min dist mapping