put the per connection socket count and ip on the normal out

[ldemailly]

put the per connection socket count and ip on the normal out so it shows up in web too. also export socket count per connection to json

fixes #601

looks like this:

# Socket and IP used for each connection:
[0]   2 socket used, resolved to 127.0.0.1:8080
[1]   2 socket used, resolved to 127.0.0.1:8080
[2]   3 socket used, resolved to 127.0.0.1:8080
[3]   2 socket used, resolved to 127.0.0.1:8080
[4]   4 socket used, resolved to 127.0.0.1:8080
[5]   5 socket used, resolved to 127.0.0.1:8080
[6]   2 socket used, resolved to 127.0.0.1:8080
[7]   2 socket used, resolved to 127.0.0.1:8080
[8]   2 socket used, resolved to 127.0.0.1:8080
[9]   3 socket used, resolved to 127.0.0.1:8080
Sockets used: 27 (for perfect keepalive, would be 10)

and json

  "Sockets": [
    1,
    1,
    1,
    1,
    1,
    1,
    1,
    2,
    1,
    1
  ],
  "SocketCount": 11,

[codecov]

Codecov Report

Merging #602 (84ab831) into master (a5d0f12) will increase coverage by 0.0%.
The diff coverage is 100.0%.

@@          Coverage Diff           @@
##           master    #602   +/-   ##
======================================
  Coverage    87.9%   87.9%           
======================================
  Files          26      26           
  Lines        3609    3611    +2     
======================================
+ Hits         3173    3175    +2     
  Misses        294     294           
  Partials      142     142           

Impacted Files	Coverage Δ
fhttp/httprunner.go	86.4% <100.0%> (+0.2%)	⬆️

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