httpboot: fix OVMF crash
httpboot: fix OVMF crash

This is a typical typo. The free operation should be done if uri
was allocated.

Signed-off-by: Lans Zhang <e5f62b0189adf41bef2a4f4e0947feed14b85bc6@windriver.com>

rhinstaller/shim,rhinstaller/shim,rhinstaller/shim