Delay CPF merge activation until all config changes have been made during unmap and enable commands; also fix some mapped IPM issues

[isc-dchui]

Fixes #1001
Fixes #1052

This is what the intro message for a namespace with mapped IPM now looks like

==================================================================================================================
|| Welcome to the Package Manager Shell (ZPM). Version: 0.10.6-SNAPSHOT (mapped from namespace 'USER')          ||
|| Enter q/quit to exit the shell. Enter ?/help to view available commands                                      ||
|| Current registry https://pm.community.intersystems.com/                                                      ||
|| System Mode: <unset>                                                                                         ||
|| Mirror Status: NOTINIT                                                                                       ||
==================================================================================================================

[isc-kiyer]

@isc-dchui just one comment but not blocking

[isc-kiyer]

Should this error status be written out instead of hiding it?

[isc-dchui]

The only errors that method will return are essentially that IPM isn't installed in or mapped to that namespace, so this is more presenting that in a clean way than hiding it.