UDS: terminate canonical path string

UDS: terminate canonical path string

When you provided a string with junk after the terminating nul to a
UNIX domain socket and used bind(2), the canonical path function would
not properly terminate the new string. This caused VFS to return
ENAMETOOLONG on an otherwise valid path name.

Test case is added to test56.

Change-Id: I883b6be23d9e4ea13c3cee28cbb3726343df037f