Merge pull request #5926 from fsateler/condition-uid

core: add ConditionUID and ConditionGID

diff --cc man/systemd.unit.xml
Simple merge

diff --cc src/core/load-fragment-gperf.gperf.m4
Simple merge

diff --cc src/shared/condition.c
Simple merge

diff --cc src/test/test-condition.c
Simple merge