Don't trace RHEL registration scripts

These scripts are littered with references to passwords and keys,
so rather than try to disable tracing in every one of those places
I propose we simply turn it off for the scripts.  This will likely
need to be revisited after the global tracing discussion is
resolved anyway.

Change-Id: I805015300bf01b2f8eec9f70ccfdf533dd9386b3
Related-Bug: 1298205

elements/rhel-common/os-refresh-config/pre-configure.d/06-rhel-registration

@@ -1,5 +1,5 @@
 #!/bin/bash
-set -eux
+set -eu
 set -o pipefail
 
 REG_ACTIVATION_KEY="$(os-apply-config --key rh_registration.activation_key --type raw --key-default '')"

elements/rhel-common/pre-install.d/00-rhel-registration

@@ -1,5 +1,5 @@
 #!/bin/bash
-set -eux
+set -eu
 set -o pipefail
 
 opts=