Fixes signing of packages.

Signing was failing as the builds
were expected to run as ubuntu but
is run as root.

Closes #11686

scripts/build/rpmmacros

 %_signature gpg
 %_signature gpg
-%_gpg_path /home/ubuntu/.gnupg
+%_gpg_path /root/.gnupg
 %_gpg_name Grafana
 %_gpg_name Grafana
 %_gpgbin /usr/bin/gpg
 %_gpgbin /usr/bin/gpg