Fix performance and bug

[masahiro331]

If this Pull Request is work in progress, Add a prefix of “[WIP]” in the title.

What did you implement:

1. Fix performance.

Fix the performance degradation introduced by this PR.
#857

This PR needs to update go.mod after vulsio/goval-dictionary#73 is merged.

2. Fix bug

[Jul  9 19:24:18]  INFO [localhost] : 0 CVEs are detected with Library
[Jul  9 19:24:18]  INFO [localhost] OVAL is fresh: redhat 6.5-x86_64
2019/07/09 19:24:18 http: panic serving 127.0.0.1:55532: runtime error: index out of range
goroutine 154 [running]:
net/http.(*conn).serve.func1(0xc000860000)
	/usr/local/Cellar/go/1.12.4/libexec/src/net/http/server.go:1769 +0x139
panic(0x51c10e0, 0x64e2980)
	/usr/local/Cellar/go/1.12.4/libexec/src/runtime/panic.go:522 +0x1b5
github.com/future-architect/vuls/oval.RedHatBase.convertToDistroAdvisory(0x53b9ac4, 0x6, 0xc001072790, 0xc0008baf90)
	/Users/01025026/work/go/src/github.com/future-architect/vuls/oval/redhat.go:157 +0x29a
github.com/future-architect/vuls/oval.RedHatBase.update(0x53b9ac4, 0x6, 0xc000876000, 0x0, 0x0, 0xc000e920f0, 0x21, 0x0, 0x0, 0x0, ...)
	/Users/01025026/work/go/src/github.com/future-architect/vuls/oval/redhat.go:136 +0x75a
github.com/future-architect/vuls/oval.RedHatBase.FillWithOval(0x53b9ac4, 0x6, 0x57be840, 0xc0006557d0, 0xc000876000, 0x510f301, 0x0, 0x0)
	/Users/01025026/work/go/src/github.com/future-architect/vuls/oval/redhat.go:51 +0x17d
github.com/future-architect/vuls/report.FillWithOval(0x57be840, 0xc0006557d0, 0xc000876000, 0xc001074680, 0x2, 0x2)
	/Users/01025026/work/go/src/github.com/future-architect/vuls/report/report.go:336 +0x44c
github.com/future-architect/vuls/report.FillCveInfo(0x57c6660, 0xc00073e500, 0x57be840, 0xc0006557d0, 0x0, 0x0, 0x0, 0x0, 0xc000876000, 0x65332e0, ...)
	/Users/01025026/work/go/src/github.com/future-architect/vuls/report/report.go:175 +0x277
github.com/future-architect/vuls/server.VulsHandler.ServeHTTP(0x57a3b80, 0xc000714460, 0xc000864000)
	/Users/01025026/work/go/src/github.com/future-architect/vuls/server/server.go:91 +0x94e
net/http.(*ServeMux).ServeHTTP(0x6513a20, 0x57a3b80, 0xc000714460, 0xc000864000)
	/usr/local/Cellar/go/1.12.4/libexec/src/net/http/server.go:2375 +0x1d6
net/http.serverHandler.ServeHTTP(0xc0000f7790, 0x57a3b80, 0xc000714460, 0xc000864000)
	/usr/local/Cellar/go/1.12.4/libexec/src/net/http/server.go:2774 +0xa8
net/http.(*conn).serve(0xc000860000, 0x57ac800, 0xc00051d600)
	/usr/local/Cellar/go/1.12.4/libexec/src/net/http/server.go:1878 +0x851
created by net/http.(*Server).Serve
	/usr/local/Cellar/go/1.12.4/libexec/src/net/http/server.go:2884 +0x2f4

Inserting redhat's oval with --no-detail option to db will panic the Title because it does not exist.
https://github.com/future-architect/vuls/blob/master/oval/redhat.go#L155-L158

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

How Has This Been Tested?

We have tested server mode.
OVAL used was redhat, ubuntu, oracle, amazon

Checklist:

• Write tests
• Write documentation
• Check that there aren't other open pull requests for the same issue/feature
• Format your source code by make fmt
• Pass the test by make test
• Provide verification config / commands
• Enable "Allow edits from maintainers" for this PR
• Update the messages below

Is this ready for review?: NO

[knqyf263]

go mod tidy, please

[masahiro331]

I'm sorry. fixed.

[knqyf263]

👍