limit gremlin endless loop

timeout when executing gremlin like this:
```
def all = g.V()
while (all.hasNext()) {
//all.next()
}
```
and cause process endless loop(jstack):
```
"gremlin-server-exec-17" #201 prio=5 os_prio=0 tid=0x00007fb77000d000 nid=0x2ebe runnable [0x00007fbb8ecf9000]
java.lang.Thread.State: RUNNABLE
at org.codehaus.groovy.runtime.callsite.PojoMetaMethodSite.checkCall(PojoMetaMethodSite.java:80)
at java_util_Iterator$hasNext.call(Unknown Source)
at Script105.run(Script105.groovy:4)
at org.apache.tinkerpop.gremlin.groovy.jsr223.GremlinGroovyScriptEngine.eval(GremlinGroovyScriptEngine.java:674)
at org.apache.tinkerpop.gremlin.groovy.jsr223.GremlinGroovyScriptEngine.eval(GremlinGroovyScriptEngine.java:376)
at javax.script.AbstractScriptEngine.eval(AbstractScriptEngine.java:233)
at org.apache.tinkerpop.gremlin.groovy.engine.GremlinExecutor.lambda$eval$0(GremlinExecutor.java:266)
at org.apache.tinkerpop.gremlin.groovy.engine.GremlinExecutor$$Lambda$55/913746983.call(Unknown Source)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at com.baidu.hugegraph.auth.HugeGraphAuthProxy$ContextTask.run(HugeGraphAuthProxy.java:282)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at java.lang.Thread.run(Thread.java:748)
```
```
"gremlin-server-exec-16" #200 prio=5 os_prio=0 tid=0x00007fb7a41be000 nid=0x2ebd runnable [0x00007fbb8edfa000]
java.lang.Thread.State: RUNNABLE
at org.codehaus.groovy.runtime.callsite.PojoMetaMethodSite$PojoMetaMethodSiteNoUnwrapNoCoerce.invoke(PojoMetaMethodSite.java:244)
at org.codehaus.groovy.runtime.callsite.PojoMetaMethodSite.call(PojoMetaMethodSite.java:53)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:119)
at Script105.run(Script105.groovy:5)
at org.apache.tinkerpop.gremlin.groovy.jsr223.GremlinGroovyScriptEngine.eval(GremlinGroovyScriptEngine.java:674)
at org.apache.tinkerpop.gremlin.groovy.jsr223.GremlinGroovyScriptEngine.eval(GremlinGroovyScriptEngine.java:376)
at javax.script.AbstractScriptEngine.eval(AbstractScriptEngine.java:233)
at org.apache.tinkerpop.gremlin.groovy.engine.GremlinExecutor.lambda$eval$0(GremlinExecutor.java:266)
at org.apache.tinkerpop.gremlin.groovy.engine.GremlinExecutor$$Lambda$55/913746983.call(Unknown Source)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at com.baidu.hugegraph.auth.HugeGraphAuthProxy$ContextTask.run(HugeGraphAuthProxy.java:282)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at java.lang.Thread.run(Thread.java:748)
```