Remove "/" sign in AbstractRestconfStreamRegistry

Remove "/" sign in AbstractRestconfStreamRegistry

In AbstractRestconfStreamRegistry#baseStreamLocation, the method generated
incorrect paths containing a double slash after `rests` in the device
notification stream URL. This error occurred because URI.getPath()
always includes a trailing slash. Additionally, the UriInfo.getBaseUri()
method, used within JaxRsRestconf, also consistently appends a slash
at the end.

Document this fact in RestconfServer and do not append it in
AbstractRestconfStreamRegistry.

JIRA: NETCONF-1274
Change-Id: Ib5074dc150d27a8482c7e49f89549973ab707270
Signed-off-by: Yaroslav Lastivka <yaroslav.lastivka@pantheon.tech>
Signed-off-by: Robert Varga <robert.varga@pantheon.tech>