Rename Runnable classes from Tasks to Actions

This is cleanup relating to a naming decision that we made awhile ago
but never got around to.
-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=117244827

java/com/google/domain/registry/dns/RefreshDnsAction.java

@@ -28,15 +28,15 @@ import com.google.domain.registry.util.Clock;
 
 import javax.inject.Inject;
 
-/** Endpoint for manually triggering refresh of DNS information. */
+/** Action that manually triggers refresh of DNS information. */
 @Action(path = "/_dr/dnsRefresh", automaticallyPrintOk = true)
-public final class RefreshDns implements Runnable {
+public final class RefreshDnsAction implements Runnable {
 
   @Inject Clock clock;
   @Inject DnsQueue dnsQueue;
   @Inject @Parameter("name") String domainOrHostName;
   @Inject @Parameter("type") TargetType type;
-  @Inject RefreshDns() {}
+  @Inject RefreshDnsAction() {}
 
   @Override
   public void run() {

java/com/google/domain/registry/dns/WriteDnsAction.java

@@ -49,9 +49,9 @@ import java.util.concurrent.Callable;
 import javax.inject.Inject;
 import javax.inject.Provider;
 
-/** Task that consumes pull-queue for zone updates to write to the DNS server. */
+/** Action that consumes pull-queue for zone updates to write to the DNS server. */
 @Action(path = "/_dr/task/writeDns", method = POST, automaticallyPrintOk = true)
-public final class WriteDnsTask implements Runnable, Callable<Void> {
+public final class WriteDnsAction implements Runnable, Callable<Void> {
 
   private static final FormattingLogger logger = FormattingLogger.getLoggerForCallerClass();
 
@@ -59,7 +59,7 @@ public final class WriteDnsTask implements Runnable, Callable<Void> {
   @Inject Provider<DnsWriter> writerProvider;
   @Inject @Config("dnsWriteLockTimeout") Duration timeout;
   @Inject @Parameter(RequestParameters.PARAM_TLD) String tld;
-  @Inject WriteDnsTask() {}
+  @Inject WriteDnsAction() {}
 
   /** Runs the task. */
   @Override