Unionfs: use braces in both branches of conditionals

Unionfs: use braces in both branches of conditionals

As per CodingStyle, if one branch of an if-then-else has braces because it
has multiple statements, then the other branch should have braces too, even
if the other branch has only one statement in it.

Signed-off-by: Erez Zadok <ezk@cs.sunysb.edu>