rpm: Fix root locations for GPG searching

rpm: Fix root locations for GPG searching

We should always look in the tools tree for /usr/share/distribution-gpg-keys,
regardless of the value of ToolsTreeCertificates= since the setting has no
impact on which /usr/share/distribution-gpg-keys directory we end up using.

We should look in the host or tools tree for /etc/pki/rpm-gpg, based on the
value of ToolsTreeCertificates=, not in the sandbox tree, because the /etc/pki
directory from the host or tools tree will always be used and mounted over the
directory from the sandbox tree, so there's no point in looking for rpm gpg keys
in the sandbox tree at all.