LSB_Test.sh: add -f option for curl

LSB_Test.sh: add -f option for curl

In normal cases when a HTTP server fails to deliver a file, it returns
an HTML document to describe the reason (e.g. 404 Not Found). The curl
will output this page as a file and do not return error. Add a "-f"
option will prevent curl from outputting that and return error.

[YOCTO #4895]

(From OE-Core rev: d53c9e6942a65f2ae5eb8f33012453c356fd6ff4)

Signed-off-by: Yi Zhao <yi.zhao@windriver.com>
Signed-off-by: Saul Wold <sgw@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>