missing libevent on coin test node

This test run complains abut "error while loading shared libraries: libevent-2.1.so.6: cannot open shared object file" , however build succeeded so this lib is on build machine.

http://coin.intra.qt.io/coin/api/results/qt/qtwebengine/8a3a5382e16f9bf7f5eafaa615473d40aac44034/LinuxUbuntu_20_04x86_64LinuxUbuntu_20_04x86_64GCCqtci-linux-Ubuntu-20.04-x86_64-50-b0499aSccache_TestOnly/4905d212e97120dcebf7e67f40ca108326af3db2/test_1620197214/log.txt.gz