Fix Travis CI on rawhide

For some reason, if we do dnf update on rawhide then the dnf install
hangs. We work around this by not doing dnf update. Hopefully the
future fixes this and we can test on fresh packages again.

.travis.test

@@ -20,8 +20,8 @@ case "$1" in
 
   fedora:*)
     [ "$1" != "fedora:23" ] && rt=compiler-rt
-    dnf -y clean all
-    dnf -y --setopt=deltarpm=0 update
+#    dnf -y clean all
+#    dnf -y --setopt=deltarpm=0 update
     dnf -y install automake autoconf libtool pkgconfig openssl-devel zlib-devel jansson-devel curl git gcc make file clang $rt
     ;;