manager cmd has chance to get result set of previous manager cmd

[irene-coming]

• dble version：
  5.6.29-dble-9.9.9.9-5c9950d-20180807061430

• configs：

schema.xml

        <schema dataNode="dn2" name="mytest" sqlMaxLimit="100">
                <table dataNode="dn1,dn3,dn4" name="test" type="global" />
                <table dataNode="dn1,dn3,dn4" name="ta" rule="hash-three" />
        </schema>

        <dataNode dataHost="172.100.9.5" database="db$1-2" name="dn$1-2" />
        <dataNode dataHost="172.100.9.6" database="db$3-4" name="dn$3-4" />

        <dataHost balance="0" maxCon="1000" minCon="3" name="172.100.9.5" slaveThreshold="100" switchType="1">
                <heartbeat>select user()</heartbeat>
                <writeHost host="hostM1" password="111111" url="172.100.9.5:3306" user="test">
                </writeHost>
        </dataHost>

        <dataHost balance="0" maxCon="1000" minCon="3" name="172.100.9.6" slaveThreshold="100" switchType="1">
                <heartbeat>select user()</heartbeat>
                <writeHost host="hostM2" password="111111" url="172.100.9.6:3306" user="test">
                </writeHost>
        </dataHost>

rule.xml

    <tableRule name="hash-three">
        <rule>
            <columns>id</columns>
            <algorithm>three-long</algorithm>
        </rule>
    </tableRule>
    <function class="Hash" name="three-long">
        <property name="partitionCount">3</property>
        <property name="partitionLength">1</property>
    </function>

server.xml

        <system>
                <property name="maxResultSet">1024</property>
        </system>

        <user name="test">
                <property name="password">111111</property>
                <property name="schemas">mytest</property>
        </user>
        <user name="root">
                <property name="password">111111</property>
                <property name="manager">true</property>
        </user>

• steps：
  step1. restart dble
  step2. execute at once:

mysql -h127.0.0.1 -uroot -p111111 -P9066
mysql> select @@date;
Query OK, 0 rows affected, 1 warning (0.01 sec)

mysql> show @@version;
ERROR 1193 (HY000): Unknown system variable 'date'
mysql> show @@version;
+--------------------------------------------+
| VERSION                                    |
+--------------------------------------------+
| 5.6.29-dble-9.9.9.9-5c9950d-20180807061430 |
+--------------------------------------------+
1 row in set (0.00 sec)

• expect result：
  1.

mysql> select @@date;
ERROR 1193 (HY000): Unknown system variable 'date'

• real result：
  1. select @@Date return success with empty resultset
  2. the next exists manager command got error for "select @@Date"

/label ~BUG

[irene-coming]

verified on dble: 5.6.29-dble-9.9.9.9-046baf4-20180817023708