mid_registrar/usrloc: Small doc improvements

Many thanks to Conrad de Wet and Devang Dhandhalya for the hints!

modules/mid_registrar/doc/mid_registrar_admin.xml

@@ -507,6 +507,9 @@ modparam("mid_registrar", "received_param", "rcv")
 		<programlisting format="linespecific">
 # NB: AVPs are cleared with every new SIP request
 modparam("mid_registrar", "extra_contact_params_avp", "$avp(extra_ct_params)")
+
+# setting the AVP during SIP message processing
+$avp(extra_ct_params) = ";transport=tls";
 </programlisting>
 		</example>
 	</section>

modules/usrloc/doc/usrloc_admin.xml

@@ -1821,8 +1821,9 @@ modparam("usrloc", "contact_refresh_timer", true)
 			</para></listitem>
 			<listitem><para>
 				<emphasis>latency</emphasis> - The latency of the last
-				successful ping for this contact. Until the first ping reply
-				for a given contact arrives, its pinging latency will be 0.
+				successful ping for this contact, in microseconds. Until the
+				first ping reply for a given contact arrives, its pinging
+				latency will be 0.
 			</para></listitem>
 			<listitem><para>
 				<emphasis>shtag</emphasis> - The shared tag of the contact,