Correct resolution of non-virtual directory names on Android

Correct resolution of non-virtual directory names on Android

* src/androidvfs.c (android_vfs_canonicalize_name): Correct
return value in cases of underflowing the directory stack.
(android_unix_name): Reset vnode operations vector of copied
vnodes to their standard value, and exclude virtual directories
from subdirectories of the root directory's parent directory.
(android_root_name): Adjust to match.