Fix for CVE-2009-2813.

Fix for CVE-2009-2813.

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== Subject:     Misconfigured /etc/passwd file may share folders unexpectedly
==
== CVE ID#:     CVE-2009-2813
==
== Versions:    All versions of Samba later than 3.0.11
==
== Summary:     If a user in /etc/passwd is misconfigured to have
==              an empty home directory then connecting to the home
==              share of this user will use the root of the filesystem
==              as the home directory.
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(cherry picked from commit 6fd272875d27c6974a194d0cb2cde39a98ca4af2)