redhat: Use a secure URL to retrieve CellServDB

redhat: Use a secure URL to retrieve CellServDB

By default, makesrpm.pl will use wget to retrieve the CellServDB
as specified in the spec file. Even though the script need not and
thus should not be run by a privileged UID, make this a bit more
secure by specifying an https URL.

Change-Id: I0f14bbac35e7dc30a6e194f8706f7f3674d15a3f
Reviewed-on: https://gerrit.openafs.org/12329
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
Tested-by: Benjamin Kaduk <kaduk@mit.edu>