When the iostream code went in it introduced a conditional that made it so the
hook event was not being raised even if a hook is present. This patch adds a
check to see if a hook is present in astman_append. If so then call into the
send_string function, which in turn raises the even for specified hook.

Also updated the ami hooks unit test, so the test could be automated.

ASTERISK-27200 #close

Change-Id: Iff37f02f9708195d8f23e68f959d6eab720e1e36