(SERVER-1453) Create helper for adding/updating TK config files
(SERVER-1453) Create helper for adding/updating TK config files

The modify_tk_config beaker command corrupts config files. This PR
adds a new helper method, `apply_one_hocon_setting`, to the test
library. It adds or updates a single hocon setting in a TK config
file. PR also adds a helper method to _remove_ a single hocon
setting, `delete_one_hocon_setting`.

shrug/puppet-server,rlinehan/puppet-server,rlinehan/puppetserver,waynr/puppet-server,waynr/puppetserver,rlinehan/puppetserver,shrug/puppet-server,briancain/puppet-server,erikPrime/puppet-server,er0ck/puppetserver,puppetlabs/puppetserver,rlinehan/puppet-server,camlow325/puppetserver,er0ck/puppetserver,briancain/puppet-server,camlow325/puppetserver,puppetlabs/puppet-server,camlow325/puppet-server,erikPrime/puppetserver,rlinehan/puppet-server,puppetlabs/puppetserver,puppetlabs/puppet-server,shrug/puppet-server,puppetlabs/puppet-server,erikPrime/puppet-server,camlow325/puppetserver,camlow325/puppet-server,rlinehan/puppetserver,waynr/puppetserver,er0ck/puppetserver,erikPrime/puppet-server,er0ck/puppetserver,puppetlabs/puppetserver,briancain/puppet-server,waynr/puppet-server,waynr/puppetserver,erikPrime/puppetserver,rlinehan/puppetserver,camlow325/puppet-server,shrug/puppet-server,erikPrime/puppetserver,waynr/puppet-server,puppetlabs/puppetserver,camlow325/puppetserver