conf: build_host is not required anymore
conf: build_host is not required anymore

Follow-up on e0b77062f9087c12f1ce504fd68104fcae3d4704

bfontecc007/osbs-client,projectatomic/osbs-client,vrutkovs/osbs-client,vrutkovs/osbs-client,DBuildService/osbs-client,projectatomic/osbs-client,bfontecc007/osbs-client,DBuildService/osbs-client