update travis.sh to support sentinel

Author: andyqzb

travis.sh

@@ -20,7 +20,7 @@ CFLAGS="-ggdb3 -O0" autoreconf -fvi && ./configure --enable-debug=log && make
 
 ln -s `pwd`/src/nutcracker  tests/_binaries/
 cp `which redis-server` tests/_binaries/
-cp `which redis-sentinel` tests/_binaries/
+cp `which redis-server` tests/_binaries/redis-sentinel
 cp `which redis-cli` tests/_binaries/
 cp `which memcached` tests/_binaries/