Resolvi o problema conforme descrito aqui:http://blog.netgloo.com/2015/07/09/spring-boot-communications-link-failure-with-mysql-and-hibernate/ , adicionando essas configurações em
application.properties Arquivo:spring.datasource.tomcat.testWhileIdle = true
spring.datasource.tomcat.timeBetweenEvictionRunsMillis = 60000
spring.datasource.tomcat.validationQuery = SELECT 1
