Fix location of version_not_found check

[headupinclouds]

• I've checked this Git style guide. [Yes]
• I've checked this CMake style guide. [Yes]
• My change will work with CMake 3.0 (minimum requirement for Hunter). [Yes]
• I will try to keep this pull request as small as possible and will try not to mix unrelated features. [Yes]

---

If a hunter_config() call specifies a VERSION that isn’t defined by a hunter_add_version() call (hunter/cmake//hunter.cmake), perhaps due to a typo, then a call to hunter_download_server_url() will be made with an empty VERSION, and the reported error looks like this:

-- [hunter *** DEBUG *** 2018-02-03T17:12:33] Foo versions available: [1.0.9999999]

[hunter ** INTERNAL **] 'hunter_download_server_url' incorrect usage
[hunter ** INTERNAL **]  option 'SHA1' with one argument is mandatory.

In this case may have asked for something like hunter_config(Foo VERSION 1.0.0), or a typo hunter_config(FOO VERSION 1.0.0y), but only a valid VERSION 1.0.9999999 exists.

This PR moves the existing HUNTER_PACKAGE_SHA1 version_not_found test above the call to hunter_download_server_url(), such that a more intuitive error is reported with the strong: "Version not found: ${ver}. See 'hunter_config' command."

With this change, the log listed above then becomes more human readable:

-- [hunter *** DEBUG *** 2018-02-03T17:15:09] FunctionalPlus versions available: [1.0.9999999]

[hunter ** FATAL ERROR **] Version not found: 1.0.0. See 'hunter_config' command.

and the developer can more easily diagnose and fix the source of the VERSION mismatch error.

[ruslo]

Released: https://github.com/ruslo/hunter/releases/tag/v0.19.244