fuse: Remove duplicate assignment

https://bugzilla.gnome.org/show_bug.cgi?id=712382
udisks2: Define SECRET_API_SUBJECT_TO_CHANGE to silence warning

https://bugzilla.gnome.org/show_bug.cgi?id=712382
udisks2: Compile function only if we have udisks >= 2.0.90

https://bugzilla.gnome.org/show_bug.cgi?id=712382
Make file-local functions static

This silences some warnings.

https://bugzilla.gnome.org/show_bug.cgi?id=712382
udisks2: Initialize variables to prevent them being used uninitialized

https://bugzilla.gnome.org/show_bug.cgi?id=712382
client: Use the correct enumeration constant

https://bugzilla.gnome.org/show_bug.cgi?id=712382