Fix NormalizeName for subpackage of unknown host

[hori-ryota]

When import unknown host package with sub, glide show following error.

when,

import:
- package: otherurl/example/root
  repo: git@otherurl:example/root.git
  vcs: git
  subpackages:
  - sub

then,

[INFO]  Downloading dependencies. Please wait...
[INFO]  --> Fetching updates for otherurl/example/root/sub.
[WARN]  otherurl/example/root/sub appears to be a vendored package. Unable to update. Consider the '--update-vendored' flag.
[ERROR] Failed to set version on otherurl/example/root/sub to : Cannot detect VCS

Because getRootFromGoGet(pkg string) string method get https://otherurl/example/root/sub and it failed.

But, fetching root is success and cached in remotePackageCache, so compare prefix to cached packages.

Does this resolve #469 ?

[mattfarina]

I'm pondering this approach and some deviations from it with semantic differences from it.

We have some cases in the past where something similar caused problems problems. I want to test those scenarios.

[hori-ryota]

@mattfarina Can I have an example if there is a useless pattern?

[hori-ryota]

@7imon7ays ping

[mattfarina]

I ran some tests and found:

• There is a performance improvement (less network calls)
• Generated glide.lock files were equivalent.