influx-toos import panic: keys must be added in sorted order

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__Steps to reproduce:__
List the minimal actions needed to reproduce the behavior.

1. Run a influxdb 1.8.6
2. Execute the following `write.sh`
```
#!/bin/bash

curl -X POST 'http://127.0.0.1:8086/query' --data-urlencode 'q=CREATE DATABASE test'

echo ""

curl -i -X POST 'http://127.0.0.1:8086/write?db=test' --data-binary \
'kpi.ebip.ret-call.cpu1,host=server02 value=0.67,id=2i,running=true,status="ok"
kpi.ebip.ret-call.\ \ .cpu1,host=server02,region=us-west value=0.55,id=2i,running=true,status="ok"
cpu1,host=server01,region=us-east,direction=in value=2.0,id=1i,running=false,status="fail"'

curl -i -X POST 'http://127.0.0.1:8086/write?db=test&precision=s' --data-binary \
'kpi.ebip.ret-call.cpu2,host=server02 float=1422568543,long=1422568544i,running=true,status="ok"
kpi.ebip.ret-call.\ \ .cpu2,host=server03,region=us-east float=1422568543702,long=1422568543703i 1422568543
cpu2,host=server04,region=us-west,direction=out float=1422568543702568543,long=1422568543702568544i,running=false,status="fail"'

curl -i -X POST 'http://127.0.0.1:8086/write?db=test&precision=h' --data-binary \
'kpi.ebip.ret-call.cpu3,host=server05,region=cn\ north,tag\ key=tag\ value idle=64,system=1i,user="Dwayne Johnson",admin=true
kpi.ebip.ret-call.\ \ .cpu3,host=server06,region=cn\ south,tag\ key=value\=with"equals" idle=16,system=16i,user="Jay Chou",admin=false
cpu3,host=server07,region=cn\ south,tag\ key=value\,with"commas" idle=74,system=23i,user="Stephen Chow"'

curl -i -X POST 'http://127.0.0.1:8086/write?db=test&precision=ms' --data-binary \
'kpi.ebip.ret-call.\ \ .cpu\ idle=14,system=31i,user="Dwayne Johnson",admin=true,character="\", ,\,\\,\\\,\\\\"
kpi.ebip.ret-call.\ \ .cpu\ idle=39,system=56i,user="Jay Chou",brief\ desc="the best \"singer\""
kpi.ebip.ret-call.\ \ .cpu\ idle=47,system=93i,user="Stephen Chow",admin=true,brief\ desc="the best \"novelist\""'

curl -i -X POST 'http://127.0.0.1:8086/write?db=test' --data-binary \
'measurement\ with\ spaces\,\ commas\ and\ "quotes",tag\ key\ with\ equals\ \==tag\ value\ with"spaces" field_k\ey\ with\ \=="string field value, multiple backslashes \,\\,\\\,\\\\"
"measurement\ with\ spaces\,\ commas\ and\ "quotes"",tag\ key\ with\ equals\ \==tag\,value\,with"commas" field_k\ey\ with\ \=="string field value, only \" need be escaped"'
```
3. Stop influxdb
4. Run influx-toos export and import: `influx_tools export -config influxdb.conf -no-conflict-path -database db -format binary | influx_tools import -config influxdb-import.conf -database test -rp autogen -build-tsi`
5. See error

__Expected behavior:__
Bug fixed

__Actual behavior:__
Panic occured

__Environment info:__

1.8.6

__Config:__
default

Reproduce the panic using the supplied write.sh data and the `influx_tools export ... | influx_tools import ...` command, with the default configuration. Start by tracing the import path that reports “keys must be added in sorted order.” Done means the provided dataset imports without a panic.

Written by the indexing model from the issue text.