Simplify functions for calls

Simplify functions for calls

For historical reasons, the call to apis was
passing the length of the api and the length
of the verb. The reason was to avoid a copy
of strings. But the copy occured only for HTTP
requests. Having this implementation is of
small interest and compromise future changes.

This patch simplify things.

Change-Id: I8157724c6c721b6797cd0eab52b07e1b8d6eb5f8
Signed-off-by: José Bollo <jose.bollo@iot.bzh>