user_channel: passwd_mgr: minor cleanup from cppcheck
user_channel: passwd_mgr: minor cleanup from cppcheck

[user_channel/passwd_mgr.cpp:220]: (style) The scope of the
variable 'userEPos' can be reduced.
[user_channel/passwd_mgr.cpp:358]: (style) The scope of the
variable 'userEPos' can be reduced.
[user_channel/passwd_mgr.cpp:444]: (style) Variable 'fd' is
assigned a value that is never used.

Tested: Not tested.
Signed-off-by: Patrick Venture <36c53fa43f47f3fd67cb2fc38031827244d18a1f@google.com>
Change-Id: If02125c422ab1e9c15c6420dbf8da6a52fb68541

openbmc/phosphor-host-ipmid,openbmc/phosphor-host-ipmid,openbmc/phosphor-host-ipmid