Update mysql 5.7 installer

tests/travis/install-mysql-5.7.sh

@@ -9,8 +9,8 @@ sudo apt-get remove "^mysql.*"
 sudo apt-get autoremove
 sudo apt-get autoclean
 echo mysql-apt-config mysql-apt-config/select-server select mysql-5.7 | sudo debconf-set-selections
-wget http://dev.mysql.com/get/mysql-apt-config_0.8.6-1_all.deb
-sudo DEBIAN_FRONTEND=noninteractive dpkg -i mysql-apt-config_0.8.6-1_all.deb
+wget http://dev.mysql.com/get/mysql-apt-config_0.8.9-1_all.deb
+sudo DEBIAN_FRONTEND=noninteractive dpkg -i mysql-apt-config_0.8.9-1_all.deb
 sudo rm -rf /var/lib/apt/lists/*
 sudo apt-get clean
 sudo apt-get update -q