Config DB is incomplete right after config load_minigraph

[andriymoroz-mlnx]

Description

Due to counters start delay if “config save” is called right after “config load_minigraph” Config DBs on disk and in memory will be different ("FLEX_COUNTER_TABLE" will be missing)

Steps to reproduce the issue:

1. config load_minigraph
2. config save (right after load_minigraph)
3. wait 3 min
4. rename /etc/sonic/config_db.json
5. config save
6. compare new /etc/sonic/config_db.json and renamed in step 4

Describe the results you received:
DB saved later will be different. "FLEX_COUNTER_TABLE"

Describe the results you expected:
Saved DBs to be the same

Additional information you deem important (e.g. issue happens only occasionally):

**Output of show version:**

SONiC Software Version: SONiC.HEAD.6-6cf2d10
Distribution: Debian 8.11
Kernel: 3.16.0-5-amd64
Build commit: 6cf2d10
Build date: Thu Sep  6 18:06:54 UTC 2018
Built by: johnar@jenkins-worker-3

**Attach debug file `sudo generate_dump`:**

```
(paste your output here)
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[yxieca]

I think the diff came 3 minutes later was due to the buffer profiles that are generated by the buffermgrd. Save them or not doesn't hurt next boot. I think it is ok.