uri: fix resolve with only port specification

Supplemented the implementation of the `src/lib/uri` parser.
Before this fix a call `uri.parse(uri.format(uri.parse(3301)))`
returned an error of 'Incorrect URI'.
Now this call return correct `service: '3301'`.
As a result, the possibility of using host=localhost by default
for `tarantoolctl connect` has been restored now.
As well as for `console.connect`.

Fixes #7479

NO_DOC=bugfix

(cherry picked from commit 96d8dcec)