influxdb: [inmem] Startup in 1.5.0 is much slower than in 1.3.5 and 1.4.2

I reopen this issue #9486 because i’ve the same behaviour with final 1.5.0 version.

Bug report

System info:

Branch	Build Time	Commit	Version
1.5	“”	“6ac835404e7e64ea7299a6eebcce1ab1ef15fe3c”	“1.5.0”

__ OS __ : Red Hat Enterprise Linux Server release 6.4 (Santiago) or CentOS Linux release 7.2.1511 (Core)

Steps to reproduce:

1. First Test in 1.3.5

[I] 2018-03-09T13:35:40Z InfluxDB starting, version 1.3.5, branch HEAD, commit 9d9001036d3585cf21925c13a57881bc6c8dcc7e
[I] 2018-03-09T13:35:40Z Go version go1.8.3, GOMAXPROCS set to 12
[I] 2018-03-09T13:35:40Z Using configuration at: /tech/influxdb/conf/influxdb.conf
...
[I] 2018-03-09T13:35:55Z /tech/influxdb/var/data/influxdb/data/telegraf/default/2323 opened in 8.036002793s service=store
...
[I] 2018-03-09T13:35:57Z Listening on HTTP:0.0.0.0:9001 service=httpd

1. Second Test in 1.4.2

[I] 2018-03-09T14:00:28Z InfluxDB starting, version 1.4.2, branch 1.4, commit 6d2685d1738277a1c2672fc58df7994627769be6
[I] 2018-03-09T14:00:28Z Go version go1.9.2, GOMAXPROCS set to 12
[I] 2018-03-09T14:00:28Z Using configuration at: /tech/influxdb/conf/influxdb.conf
...
[I] 2018-03-09T14:00:44Z /tech/influxdb/var/data/influxdb/data/telegraf/default/2323 opened in 8.537640076s service=store
...
[I] 2018-03-09T14:00:47Z Listening on HTTP:0.0.0.0:9001 service=httpd

1. Third test in 1.5.0

ts=2018-03-09T13:43:45.145501Z lvl=info msg="InfluxDB starting" log_id=06jktnzG000 version=1.5.0 branch=1.5 commit=6ac835404e7e64ea7299a6eebcce1ab1ef15fe3c
ts=2018-03-09T13:43:45.145557Z lvl=info msg="Go runtime" log_id=06jktnzG000 version=go1.9.2 maxprocs=12
...
ts=2018-03-09T13:54:22.970753Z lvl=info msg="Opened shard" log_id=06jktnzG000 service=store trace_id=06jktnzl000 op_name=tsdb_open path=/tech/influxdb/var/data/influxdb/data/telegraf/default/2323 duration=251247.336ms
...
ts=2018-03-09T13:54:33.583256Z lvl=info msg="Listening on HTTP" log_id=06jktnzG000 service=httpd addr=0.0.0.0:9001 https=false

Expected behavior: [What you expected to happen]

Same startup time in all versions

Actual behavior: [What actually happened]

Release	Total startup time	One shard open time
1.3.5	17s	8.036002793s
1.4.2	19s	8.537640076s
1.5.0	11min	251247.336ms

We made a test in 1.5.0 with tsi1 enabled (after influx_inspect buildtsi command) and we have the same result.