component/serf: Use openssl == 1.0

Since default openssl component is 1.1 and is not compatible with this
component, use openssl-1.0.

component/serf/buildout.cfg

@@ -15,7 +15,7 @@ md5sum = 4f8e76c9c6567aee1d66aba49f76a58b
 configure-options =
   --with-apr=${apache:location}/bin/apr-1-config
   --with-apr-util=${apache:location}/bin/apu-1-config
-  --with-openssl=${openssl:location}
+  --with-openssl=${openssl-1.0:location}
 environment =
   CFLAGS=-I${zlib:location}/include -I${libuuid:location}/include
   LDFLAGS=-L${zlib:location}/lib -Wl,-rpath=${zlib:location}/lib -L${libuuid:location}/lib -Wl,-rpath=${libuuid:location}/lib