functions: Added function to enable custom module

Enrico Bocchi requested to merge ebocchi/rpmci:module-enable into master

As described in RQF2361514, a recent release of Ceph Quincy requires libarrow-devel and parquet-libs-devel, which express a dependency against utf8proc-devel. This latter is excluded by yum/dnf because of is filtered out by modular filtering. Enabling module 'subversion-devel' allows pulling in utf8proc-devel.

Code is untested.

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