uhttpd: fix connection hangs

git-svn-id: svn://svn.openwrt.org/openwrt@35290 3c298f89-4303-0410-b956-a3cf2f4a3e73
uhttpd: fix another small hang issue with the same symptoms

git-svn-id: svn://svn.openwrt.org/openwrt@35291 3c298f89-4303-0410-b956-a3cf2f4a3e73