Proper behavior of resolvePath()

the path need to be normalized before putting it into resolvePath()
otherwise the returned internalPath will not match followup calls to e.g. Cache::getID()

fixes #5255

````
dav:/oc/core/remote.php/webdav/test/> cd ..
dav:/oc/core/remote.php/webdav/> propget .
Fetching properties for `.':
DAV: getetag = "5256b3c6ecf55"
DAV: getlastmodified = Thu, 10 Oct 2013 14:03:15 GMT
DAV: resourcetype = <DAV:collection></DAV:collection>
DAV: quota-used-bytes = 17030195
DAV: quota-available-bytes = 80326975488
dav:/oc/core/remote.php/webdav/> cd test 
dav:/oc/core/remote.php/webdav/test/> put README.md 
Uploading README.md to `/oc/core/remote.php/webdav/test/README.md':
Progress: [=============================>] 100,0% of 981 bytes succeeded.
dav:/oc/core/remote.php/webdav/test/> cd ..
dav:/oc/core/remote.php/webdav/> propget .
Fetching properties for `.':
DAV: getetag = "5256b3f394aa6"
DAV: getlastmodified = Thu, 10 Oct 2013 14:04:31 GMT
DAV: resourcetype = <DAV:collection></DAV:collection>
DAV: quota-used-bytes = 17030195
DAV: quota-available-bytes = 80326946816
dav:/oc/core/remote.php/webdav/>