Well, I tried to do so using instruction you mentioned. There is something missing in apache2 installation and apxs is not able to build fully functional mod_auth_kerb.so. During building there was warings, see below:
Additionally when the build was done, apache was not starting and below logs were generated.
httpd.bin: Syntax error on line 162 of /opt/redmine-4.1.0-8/apache2/conf/httpd.conf: Cannot load modules/modauth_kerb.so into server: /opt/redmine-4.1.0-8/apache2/modules/mod_auth_kerb.so: undefined symbol: krb5_rc_dfl_init_
apache config test fails, aborting
As a result I cannot build the mod_auth_kerb.so. This is why I request to add it permanently into bitnami bundle. Kerberos also increases domain login security as no password is sent through the network.