specifically change the expectation of the code to be such that the node-url
(self.url) always includes the trailing slash to be a correctly formed url
moreover read the node-url from the 'node.url' file found in the node 'basedir'
and only if that doesn't exist, then fall back to reading the 'webport' file
from therein and assuming localhost. This then supports the general tahoe
pattern that tools needing only a webapi server can be pointed at a directory
containing the node.url file, which can optionally point to another server,
rather than requiring a complete node dir and locally running node instance.
from testing on linux (specifically ubuntu hardy) the libfuse dll has a
different name, specifically libfuse.so.2. this patch tries libfuse.so
and then falls back to trying .2 if the former fails.
it also changes the unmount behaviour, to simply return from the handler's
loop_forever() loop upon being unmounted, rather than raising an EOFError,
since none of the client code I looked at actually handled that exception,
but did seem to expect to fall off of main() when loop_forever() returned.
Additionally, from my testing unmount typically led to an OSError from the
fuse fd read, rather than an empty read, as the code seemed to expect.
also removed a spurious import pyflakes quibbled about.
