To block packages from upgrading, you can use command apt-mark hold.
apt-mark hold PKG_NAME
Example
apt-mark hold libtomcat8-java tomcat8 tomcat8-admin tomcat8-common
To list packages that are on hold, run
root@ip-172-26-8-193:~# apt-mark showhold libtomcat8-java tomcat8 tomcat8-admin tomcat8-common root@ip-172-26-8-193:~#
If you want to remove block, you can use apt-mark unhold command.
apt-mark unhold libtomcat8-java tomcat8 tomcat8-admin tomcat8-common
