client: Made sure that the external fuse_interrupt() function won't be called from our own threads.

Therefore, the static interrupt query function was moved into the Options class. The libxtreemfs' internal threads now use a copy of the client's Options with disabled interrupt and retry functionality (the latter one is relevant when resolving UUIDs to addresses).

git-svn-id: https://xtreemfs.googlecode.com/svn/trunk@3212 f8528748-c2c0-11dd-ba5c-d3b7c2b3b534