loadSample fails on 2nd init (or reinstall).

T=testlib1
curl -HX-Okapi-Url:http://localhost:8081 -HX-Okapi-Tenant:$T \
   -d'{"module_to":"mod-permissions-0.1.0","parameters":[{"key":"loadSample", "value":"true"}]}' \
   -HContent-Type:application/json http://localhost:8081/_/tenant

9:36:29 [] [testlib1] [] [mod_permissions] ERROR TenantLoading        POST http://localhost:8081/perms/users returned status 400: ERROR: duplicate key value violates unique constraint "permissions_users_userid_idx_unique" (23505)
19:36:29 [] [testlib1] [] [mod_permissions] ERROR PermsAPI             Error updating derived fields: ERROR: duplicate key value violates unique constraint "permissions_users_userid_idx_unique" (23505)
io.vertx.pgclient.PgException: ERROR: duplicate key value violates unique constraint "permissions_users_userid_idx_unique" (23505)
	at io.vertx.pgclient.impl.codec.ErrorResponse.toException(ErrorResponse.java:31) ~[mod-permissions-fat.jar:?]
	at io.vertx.pgclient.impl.codec.QueryCommandBaseCodec.handleErrorResponse(QueryCommandBaseCodec.java:57) ~[mod-permissions-fat.jar:?]
	at io.vertx.pgclient.impl.codec.ExtendedQueryCommandCodec.handleErrorResponse(ExtendedQueryCommandCodec.java:90) ~[mod-permissions-fat.jar:?]
	at io.vertx.pgclient.impl.codec.PgDecoder.decodeError(PgDecoder.java:246) ~[mod-permissions-fat.jar:?]
	at io.vertx.pgclient.impl.codec.PgDecoder.decodeMessage(PgDecoder.java:132) [mod-permissions-fat.jar:?]
	at io.vertx.pgclient.impl.codec.PgDecoder.channelRead(PgDecoder.java:112) [mod-permissions-fat.jar:?]
	at io.netty.channel.CombinedChannelDuplexHandler.channelRead(CombinedChannelDuplexHandler.java:251) [mod-permissions-fat.jar:?]
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:379) [mod-permissions-fat.jar:?]
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:365) [mod-permissions-fat.jar:?]
	at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:357) [mod-permissions-fat.jar:?]
	at io.netty.channel.DefaultChannelPipeline$HeadContext.channelRead(DefaultChannelPipeline.java:1410) [mod-permissions-fat.jar:?]
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:379) [mod-permissions-fat.jar:?]
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:365) [mod-permissions-fat.jar:?]
	at io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:919) [mod-permissions-fat.jar:?]
	at io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.read(AbstractNioByteChannel.java:166) [mod-permissions-fat.jar:?]
	at io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:722) [mod-permissions-fat.jar:?]
	at io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:658) [mod-permissions-fat.jar:?]
	at io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:584) [mod-permissions-fat.jar:?]
	at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:496) [mod-permissions-fat.jar:?]
	at io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:986) [mod-permissions-fat.jar:?]
	at io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74) [mod-permissions-fat.jar:?]
	at io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30) [mod-permissions-fat.jar:?]