get_sysfs_attr_as_double_uncached

Look up the sysfs attribute with name on this and convert it to a double precision floating point number using ascii_strtod.

This function does blocking I/O, and updates the sysfs attributes cache.

Before version 238 the uncached getters would not strip trailing newlines.

Parameters:

this	A Device.
name	Name of the sysfs attribute.

Returns:

The value of the sysfs attribute or 0.0 if there is no such attribute.