fix: wait for output reading to complete before parsing version

NodeInstall.getVersion currently does not block waiting for STDOUT and STDERR
to be read completely. This causes random failure during node
installation because of forcing an empty version.
This change waits for future to complete before parsing the version
value.

flow-server/src/main/java/com/vaadin/flow/server/frontend/installer/NodeInstaller.java

@@ -26,6 +26,7 @@
 import java.util.Arrays;
 import java.util.List;
 import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.ExecutionException;
 
 import org.apache.commons.io.FileUtils;
 import org.slf4j.Logger;
@@ -559,8 +560,14 @@ private static FrontendVersion getVersion(String tool,
                 throw new IOException("Process exited with non 0 exit code. ("
                         + exitCode + ")");
             }
-            return FrontendUtils.parseFrontendVersion(
-                    streamConsumer.getNow(new Pair<>("", "")).getFirst());
+            String version;
+            try {
+                version = streamConsumer.get().getFirst();
+            } catch (ExecutionException e) {
+                getLogger().debug("Cannot read {} version", tool, e);
+                version = "";
+            }
+            return FrontendUtils.parseFrontendVersion(version);
         } catch (InterruptedException | IOException e) {
             throw new InstallationException(String.format(
                     "Unable to detect version of %s. %s", tool,