gui: Hide "Failed Items" unless there is an actual failure (fixes #3647)

Since delta indexes it's perfectly normal for us to need files that are
currently unavailable due to devices being disconnected. This doesn't
imply a failure, so we should not show the "Failed Items" line and
corresponding eternal spinner (since it would never be filled in, since
there is no failure).

We still show state "Out of Sync" (correct) and the list of files we
need (correct).

test/h1/config.xml

@@ -1,4 +1,4 @@
-<configuration version="15">
+<configuration version="16">
     <folder id="default" label="" path="s1/" type="readwrite" rescanIntervalS="10" ignorePerms="false" autoNormalize="true">
         <device id="I6KAH76-66SLLLB-5PFXSOA-UFJCDZC-YAOMLEK-CP2GB32-BV5RQST-3PSROAU"></device>
         <device id="MRIW7OK-NETT3M4-N6SBWME-N25O76W-YJKVXPH-FUMQJ3S-P57B74J-GBITBAC"></device>

test/h2/config.xml

@@ -1,4 +1,4 @@
-<configuration version="15">
+<configuration version="16">
     <folder id="default" label="" path="s2/" type="readwrite" rescanIntervalS="15" ignorePerms="false" autoNormalize="true">
         <device id="I6KAH76-66SLLLB-5PFXSOA-UFJCDZC-YAOMLEK-CP2GB32-BV5RQST-3PSROAU"></device>
         <device id="MRIW7OK-NETT3M4-N6SBWME-N25O76W-YJKVXPH-FUMQJ3S-P57B74J-GBITBAC"></device>
@@ -75,7 +75,7 @@
         <localAnnounceEnabled>true</localAnnounceEnabled>
         <localAnnouncePort>21027</localAnnouncePort>
         <localAnnounceMCAddr>[ff12::8384]:21027</localAnnounceMCAddr>
-        <maxSendKbps>0</maxSendKbps>
+        <maxSendKbps>10</maxSendKbps>
         <maxRecvKbps>0</maxRecvKbps>
         <reconnectionIntervalS>5</reconnectionIntervalS>
         <relaysEnabled>true</relaysEnabled>
@@ -96,7 +96,7 @@
         <cacheIgnoredFiles>false</cacheIgnoredFiles>
         <progressUpdateIntervalS>5</progressUpdateIntervalS>
         <symlinksEnabled>true</symlinksEnabled>
-        <limitBandwidthInLan>false</limitBandwidthInLan>
+        <limitBandwidthInLan>true</limitBandwidthInLan>
         <minHomeDiskFreePct>1</minHomeDiskFreePct>
         <releasesURL>https://upgrades.syncthing.net/meta.json</releasesURL>
         <overwriteRemoteDeviceNamesOnConnect>false</overwriteRemoteDeviceNamesOnConnect>