Use "se" instead of "f" for fuse_session pointer where possible.

Use "se" instead of "f" for fuse_session pointer where possible.

These changes were generated with the following Coccinelle semantic
patch:

@@
symbol f, se; // avoid unneeded warnings from Coccinelle
@@
struct fuse_session *
-f
+se
 ;
<...
-f
+se
...>

@@
identifier fn;
@@
fn(...,struct fuse_session *
-f
+se
,...) { <...
-f
+se
...> }