Fix daemonization command status test

In bin/elasticsearch, we grep the command line looking for various flags
that indicate the process should be daemonized. To do this, we simply
test command status from the grep. Sadly, this is utterly broken
(unreleased) as instead we are testing the output of the command, not
the command status. This commit fixes this issue.

Relates #26196

distribution/src/main/resources/bin/elasticsearch

@@ -27,7 +27,7 @@ ES_JVM_OPTIONS="$CONF_DIR"/jvm.options
 ES_JAVA_OPTS="`parse_jvm_options "$ES_JVM_OPTIONS"` $ES_JAVA_OPTS"
 
 # manual parsing to find out, if process should be detached
-if [ ! `echo $* | grep -E '(^-d |-d$| -d |--daemonize$|--daemonize )'` ]; then
+if ! echo $* | grep -E '(^-d |-d$| -d |--daemonize$|--daemonize )' > /dev/null; then
   exec \
     "$JAVA" \
     $ES_JAVA_OPTS \