Fix and use kadm5 setkey test program

Fix and use kadm5 setkey test program

Fix build errors in setkey-test.c and add Makefile rules to build and
run it.  Adjust the kadmin test environment to create the principal
"testkeys" for use by the test-setkey-client rule, and to set
allow_weak_crypto as setkey-test.c sets DES keys.

ticket: 8355