Added fallback for mysql-client when using MariaDB (#110)

* Fized mysql-client installation error with existing MariaDB server

* Fized permissions

* Changed command availability detection

guac-install.sh

@@ -199,6 +199,9 @@ if [[ "${NAME}" == "Ubuntu" ]]; then
     fi
     if [ "$installMySQL" = true ]; then
         MYSQL="mysql-server mysql-client mysql-common mysql-utilities"
+    # Checking if (any kind of) mysql-client or compatible command installed. This is useful for existing mariadb server
+    elif type "mysql" > /dev/null; then
+	MYSQL=""
     else
         MYSQL="mysql-client"
     fi