Description of problem:
If a directory is provided as the location of the satellite cert, the installer
dies.  It should be a bit more tolerant.


Steps to Reproduce:
1. Start install (ie ./install.pl --disconnected --skip-db-population
--skip-db-install)
2. When prompted for a cert give a dir ( /root, /, /etc)

  
Actual results:
* Activating Satellite.
Where is your satellite certificate file? /root
** Loading Satellite Certificate.
Use of uninitialized value in sprintf at install/install_main.pl line 2237.
No data found in ''.


Expected results:
Warning data provided is a dir, not a file.