Fix the API compatibility of "UriMatcher#addURI"

The previous patch (ef23bf19 Allow leading slash in path...) made
a single slash path unmatchable.
To solve it, this patch stops removing a slash character if the path
only has a slash character.
Now, a single slash is a matchable path for a URI without path string.

Bug: 29524484
Change-Id: I90b357aa48be1a3e0cf36e75ed2a9d6532908972
2 files changed