Make find_many_at_once private; explain ActiveState dependency.

library/systemd/src/lib/yast2/systemd_unit.rb

@@ -41,8 +41,14 @@ class SystemdUnit
     #
     # systemctl.c:check_unit_active uses (active, reloading)
     # For bsc#884756 we also consider "activating" to be active.
-    #
     # (The remaining states are "deactivating", "inactive", "failed".)
+    #
+    # Yes, depending on systemd states that are NOT covered by their
+    # interface stability promise is fragile.
+    # But: 10 to 50ms per call of systemctl is-active, times 100 to 300 services
+    # (depending on hardware and software installed, VM or not)
+    # is a 1 to 15 second delay (bsc#1045658).
+    # That is why we try hard to avoid many systemctl calls.
     ACTIVE_STATES = ["active", "activating", "reloading"].freeze
 
     # A Property Map is a plain Hash(Symbol => String).

library/systemd/src/modules/systemd_service.rb

@@ -91,9 +91,12 @@ def find!(service_name, propmap = {})
 
     # @param service_names [Array<String>] "foo" or "foo.service"
     # @param propmap [SystemdUnit::PropMap]
-    # @return [Array<Service,nil>] `nil` if not found, [] if no can do
-    # @raise [SystemdServiceNotFound] if an unexpected problem occurs
-    def find_many_at_once(service_names, propmap = {})
+    # @return [Array<Service,nil>] `nil` if a service is not found,
+    #   [] if this helper cannot be used:
+    #   either we're in the inst-sys without systemctl,
+    #   or it has returned fewer services than requested
+    #   (and we cannot match them up)
+    private def find_many_at_once(service_names, propmap = {})
       return [] if Stage.initial
 
       snames = service_names.map { |n| n + UNIT_SUFFIX unless n.end_with?(UNIT_SUFFIX) }