Packages in MariaDB 10.2 repository for SLES12-ppc64le are not sufficient to satisfy all the dependencies.
Gelera depends on two packages from IBM "Advance Toolchain":
1) runtime package
2) mcore-libs package
The first one is included in the MariaDB repo. But the second one is missing. Meanwhile, it's needed to provide the Boost libraries ('garbd' daemon depends on Boost "Program options" library).
Please consider adding "mcore-libs" to the repository.