v2api: pass fusedebug option via MountOptions
v2api: pass fusedebug option via MountOptions

srv.SetDebug() is deprecated and only enables the debug
output after the init sequence, so we missed the first
few transaction in the debug output.

rfjakob/gocryptfs,rfjakob/gocryptfs,rfjakob/gocryptfs,rfjakob/gocryptfs