logger: do not interpret encoded url in error as format string

[kannappanr]

Description

While logging an error, it interprets encoded url in the error as a format string.

Motivation and Context

API: SYSTEM()
Time: 14:42:31 PST 01/16/2019
Error: Post http://minio-02:9000/minio/storage/v2/media/nvme5/test/appendfile?file-path=342e7d74-206b-4cd6-9143-955e73e6835d%!F(MISSING)part.1&volume=.minio.sys%!F(MISSING)tmp: EOF
       1: cmd/bitrot.go:185:cmd.(*bitrotWriter).Append()
       2: cmd/erasure-encode.go:48:cmd.(*parallelWriter).Append.func1()

Regression

No

How Has This Been Tested?

I tested this by modifying the minio binary, to log an error
logger.LogIf(context.Background(), errors.New("%s test"))

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added unit tests to cover my changes.
• I have added/updated functional tests in mint. (If yes, add mint PR # here: )
• All new and existing tests passed.

[codecov]

Codecov Report

Merging #7110 into master will increase coverage by 0.18%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #7110      +/-   ##
==========================================
+ Coverage   52.18%   52.37%   +0.18%     
==========================================
  Files         265      275      +10     
  Lines       32858    42959   +10101     
==========================================
+ Hits        17146    22498    +5352     
- Misses      13631    18378    +4747     
- Partials     2081     2083       +2

Impacted Files	Coverage Δ
cmd/http/conn_bug_21133.go	66.66% <0%> (-8.34%)	⬇️
cmd/gateway-main.go	15.53% <0%> (-7.35%)	⬇️
main.go	50% <0%> (-7.15%)	⬇️
pkg/madmin/utils.go	16.66% <0%> (-7.15%)	⬇️
cmd/config-dir.go	40.74% <0%> (-7.09%)	⬇️
cmd/globals.go	55.88% <0%> (-7.09%)	⬇️
cmd/auth-handler.go	67.89% <0%> (-6.01%)	⬇️
cmd/lock-rpc-server.go	30.76% <0%> (-6%)	⬇️
cmd/service.go	21.42% <0%> (-5.85%)	⬇️
cmd/server-rlimit.go	54.16% <0%> (-5.84%)	⬇️
... and 242 more

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[harshavardhana]

LGTM

[minio-ops]

Error running mint automation
+ mkdir -p 7110-ce55943/gopath/src/github.com/minio
+ git clone --quiet https://github.com/minio/minio.git 7110-ce55943/gopath/src/github.com/minio/minio
fatal: unable to access 'https://github.com/minio/minio.git/': Could not resolve host: github.com; Unknown error