Windows agent was giving empty output for section Skype for a number of reasons for all agent versions since 1.4.0:
* Windows registry was queried with an illegal parameter REG_MULTI_SZ passed to RegOpenKeyExW. Starting from Windows Server 2016, this illegal parameter caused the query to fail with "access denied".
* Werk #4007 fix (commit b89af681c90) caused the entire Skype section to fall out if querying any of the subsection queries to Windows registry failed. Werk #4007 was fixed based on the incorrect assumption that Skype performance counters were queried over WMI. In fact, they query Windows registry PerfLib instead of WMI.
* The perf counter name "LS:JoinLauncher - Join Launcher Service Failures" was misspelled in singular, causing also this query to fail. This subsection had never been working correctly.
* On master branch, the refactoring done in 6946cb0b8e12b5a41c24a9e02c0f5fd472b214df broke the resolving of counter base numbers based on their names.
These causes of failure are now fixed in Windows agent. The spelling of LS:JoinLauncher is also corrected in Skype check code.
The performance of Skype perf counter queries got awkward after reverting Werk #4007, that is, executing all of the subsection queries even if some of them failed due to missing perf counters. This is now fixed by mapping the perf counters names to their counter base numbers once and reusing this mapping for all desired perf counters. This avoids the unnecessary looping through Windows registry for each perf counter separately.
New log entries are now being made for functionality related to perf counters in order to make debugging easier.