duplicate metrics with same name and label values

[salapat11]

MQ version: 9.0.0.3
mq-golang: Dev branch
Go: go1.11 linux/amd64

Using the mq-golang and mq-metric-samples/mq-prometheus libraries for collecting metrics. Compile and install worked fine and the exporter started with no issues. However, errors happen as below when calling the metrics endpoint -

An error has occurred during metrics collection:

5 error(s) occurred:

collected metric ibmmq_qmgr_interval_mqput_mqput1_total label:<name:"qmgr" value:"xxxxx" > gauge:<value:xxx > was collected before with the same name and label values
collected metric ibmmq_object_mqget_count label:<name:"object" value:"xxxx" > label:<name:"qmgr" value:"xxx" > gauge:<value:xx > was collected before with the same name and label values

[ibmmqmet]

I think this should be fixed with the latest push in #63. Looks like newer Prometheus versions were flagging an error that older versions accepted blindly.

[salapat11]

Thanks for the fix. Will merge the code