Sometimes the gpg script when run inside an improperly configured

Sometimes the gpg script when run inside an improperly configured
vserver (i.e., one where mknod fails.).  Two improvements to the
script:

- remove zero length *.gpg files, as those are turds left over from a
  failed gpg command.

- add in a "check" after the mknod command to have the script fail
  more gracefully.