budb: Store dumper information correctly

Change f498c18a6f7300eb89ca3b9d9b85c4d461fa8474 attempted to fix
a problem with using an inappropriate function to copy the
ktc_principal value 'principal' into the d.dumper structure element.

Originally the code read:
    principal_hton(&principal, &d.dumper)

which copies the 'host' principal principal into the 'net' structure
d.dumper. However, this was changed to
    principal = d.dumper

Which populates 'principal' with whatever garbage is in the d.dumper
structure.

Fix this so that the assignment is done the right way around.

Caught by clang-analyzer

Reviewed-on: http://gerrit.openafs.org/9252
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
(cherry picked from commit dce2d8206ecd35c96e75cc0662432c2a4f9c3d7a)

Change-Id: Ib3851649293bddedf465739acc9bd7ad327c80e0
Reviewed-on: http://gerrit.openafs.org/9537
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>
Reviewed-by: Andrew Deason <adeason@sinenomine.net>
Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>