scouting: Make background_task interval configurable

This patch modifies the API so that the background task gets invoked
at a user-defined interval. There are no functional changes since we
schedule everything at 10 minute intervals. That matches the previous
behaviour.

Signed-off-by: Philipp Schrader <philipp.schrader@gmail.com>
Change-Id: I512ddcd01408f9d1af706ca390c84368f6816638
diff --git a/scouting/webserver/main.go b/scouting/webserver/main.go
index ba9d120..c5bed2c 100644
--- a/scouting/webserver/main.go
+++ b/scouting/webserver/main.go
@@ -141,17 +141,17 @@
 	// Since Go doesn't support default arguments, we use 0 and "" to
 	// indicate that we want to source the values from the config.
 
-	matchListScraper := background_task.BackgroundTask{}
+	matchListScraper := background_task.New(10 * time.Minute)
 	matchListScraper.Start(func() {
 		match_list.GetMatchList(database, 0, "", *blueAllianceConfigPtr)
 	})
 
-	rankingsScraper := background_task.BackgroundTask{}
+	rankingsScraper := background_task.New(10 * time.Minute)
 	rankingsScraper.Start(func() {
 		rankings.GetRankings(database, 0, "", *blueAllianceConfigPtr)
 	})
 
-	driverRankingParser := background_task.BackgroundTask{}
+	driverRankingParser := background_task.New(10 * time.Minute)
 	driverRankingParser.Start(func() {
 		// Specify "" as the script path here so that the default is
 		// used.