hostlist: factor out a pattern

This is a clerical patch which transforms a repeating pattern of type

 	if (dims > 1) {
		if (hr->width == dims) {
			// Alternative 'A'
		} else {
			// Alternative 'B'
		}
	} else {
		// Alternative 'B'
	}

into the shorter pattern

	if (dims > 1 && hr->width == dims) {
		// Alternative 'A'
	} else {
		// Alternative 'B'
	}