Add --api to the configure host part

[martbhell]

No description provided.

[nitisht]

@martbhell can you please explain why is this needed?

[martbhell]

Hello @nitisht for our ceph RGW S3 endpoint it doesn't work without --api:

$ ./mc config host add pouta https://object.pouta.csc.fi:443 myaccesskey mysecretkey S3v2
mc:  Unable to initialize new config from the provided credentials. The access key ID you provided does not exist in our records.
$ ./mc config host add pouta https://object.pouta.csc.fi:443 myaccesskey mysecretkey --api S3v2
Added `pouta` successfully.

Is it enough to explain in here or would you like it in the commit too?

[codecov]

Codecov Report

Merging #2555 into master will decrease coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff            @@
##           master   #2555      +/-   ##
=========================================
- Coverage   10.62%   10.6%   -0.02%     
=========================================
  Files         106     106              
  Lines       10723   10723              
=========================================
- Hits         1139    1137       -2     
- Misses       9434    9436       +2     
  Partials      150     150

Impacted Files	Coverage Δ
cmd/pipechan.go	95.12% <0%> (-4.88%)	⬇️

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[vadmeste]

LGTM