exclude_retention_policy_tag and exclude_database_tag excludes both DB and RP tags from metrics even if the other exclude_ parameter is set to false

[abalone23]

Relevant telegraf.conf:

 database_tag = "thedb"
## If true, the database tag will not be added to the metric.
  # exclude_database_tag = false

 retention_policy_tag = "therp"
 ## If true, the 'retention_policy_tag' will not be removed from the metric.
  exclude_retention_policy_tag = true

System info:

telegraf 1.14

Steps to reproduce:

1. Set exclude_retention_policy_tag = true and exclude_database_tag = false (or vice-versa)
2. curl -i -XPOST 'http://localhost:8186/write' --data-binary 'cpu_load_short,thedb=mydb,therp=one_week,host=server01,region=us-west value=0.65 1586387198000700200'

Expected behavior:

> select * from cpu_load_short
name: cpu_load_short
time                host     region  thedb    value
----                ----     ------  -----    -----
1586387198000700200 server01 us-west mydb 0.65

Actual behavior:

> select * from cpu_load_short
name: cpu_load_short
time                host     region  value
----                ----     ------  -----
1586387198000700200 server01 us-west 0.65

Additional info:

exclude_retention_policy_tag should only exclude the rp
exclude_database_tag should only exclude the db

[reimda]

related to #7308