Fix make dist by finishing RPM cleanup

Summary: D5258 was incomplete, did not have an appropriate test plan, and broke make dist as a result.

Test Plan:

./autogen.sh
mkdir build && cd build
../configure
make dist

Reviewers: #bitcoin_abc, deadalnix, Fabien

Reviewed By: #bitcoin_abc, deadalnix, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D5376