Change the code of open_and_lseek() to make sure that opened file is
closed in every failure path as well. While at it make sure we don't
mix returning function return code and returning errno by opting to
always return the former.

Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>