localrepo: use path expansion API via vfs
As a part of migration to vfs, this patch moves path expansion API
invocations in the constructor of "localrepository" to the constructor
of "opener", because the root path to the repository is very important
to handle paths using non-ASCII characters correctly.
This patch also rearrange initialization order of "wvfs" field,
because it is required to initialize "self.root".
http://mercurial.selenic.com/bts/issue1438
$ "$TESTDIR/hghave" symlink || exit 80
$ hg init
$ ln -s foo link
$ hg add link
$ hg ci -mbad link
$ hg rm link
$ hg ci -mok
$ hg diff -g -r 0:1 > bad.patch
$ hg up 0
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg import --no-commit bad.patch
applying bad.patch
$ hg status
R link
? bad.patch