Description of problem:
SystemManagerRemote.setSystemConfiguration() method assumes that the Properties passed to it contain a superset of all the properties that are already defined in the database (i.e. it correctly handles the scenarios where the properties passed to it contain the same names or contain the same names and some new ones).

The cached properties that are then used in other places in the code are assigned to a copy of properties passed to this method. This results in the fact that the properties that are in the database but weren't in the passed in properties suddenly seem to have disappeared even though they are still present in the database.

This condition is intermittent because the system config cache is being reloaded every minute but still opens a window where the business layer reports inconsistent data.

Because setSystemConfiguration() is a remote method we should make it as robust as possible.

How reproducible:
always

Steps to Reproduce:
1.Using the CLI, log in as a user having at least MANAGE_SETTINGS privs:
var props = SystemManager.systemConfiguration;
pretty.print(props.get("CAM_BASE_URL");//prints out the URL of the server
props.remove("CAM_BASE_URL");
SystemManager.setSystemConfiguration(props, false);
props = SystemManager.systemConfiguration;
pretty.print(props.get("CAM_BASE_URL"); //prints nothing
//.... wait a couple of minutes
props = SystemManager.systemConfiguration;
pretty.print(props.get("CAM_BASE_URL"); //prints the URL again
  
Actual results:
see steps

Expected results:
no inconsistency in the reported properties

Additional info: