sanitize / as separator between project and package on osc command line

[e4t]

Project and package may be separated by a space or slash '/' on the command line of the obs CLI. When parsing the command line what happens is that the parser interprets project/package as one argument (as the project) and passes this to a URL builder. In the URI project and package are separated by a single '/', thus a 'foo/bar' will be interpreted as a project 'foo' with package 'bar'. However, specifying multiple consecutive '/' may lead to unintended results: the form 'foo//bar' is passed up to the backend which isn't able to handle the '//' gracefully:
osc copypac -e -K openSUSE:Factory coreutils home://coreutls.Factory
may lead to all of Factory being copied over to ones home.
Since the slash is used as a directory separator in paths where multiple slashes are collapsed to one, it is not ruled out that this mistake happens.
Thus a sanitation of '/' characters should occur before they are placed into an URL.