Remove "registertrying" and add "rtp_engine" from/to sip.conf.sample

The "registertrying" option was removed in r343220. The "rtp_engine"
option was added in r186078 but erroneously named "engine" in the sample.
Note that there is no global sip setting for a different engine.
........

Merged revisions 381668 from http://svn.asterisk.org/svn/asterisk/branches/1.8


git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/11@381669 65c4cc65-6c06-0410-ace0-fbb531ad65f3

configs/sip.conf.sample

@@ -457,7 +457,7 @@ srvlookup=yes                   ; Enable DNS SRV lookups on outbound calls
                                        ; register their phones.
 ;contactacl=named_acl_example          ; Use named ACLs defined in acl.conf
 
-;engine=asterisk                ; RTP engine to use when communicating with the device
+;rtp_engine=asterisk            ; RTP engine to use when communicating with the device
 
 ;
 ; If regcontext is specified, Asterisk will dynamically create and destroy a
@@ -1233,7 +1233,6 @@ srvlookup=yes                   ; Enable DNS SRV lookups on outbound calls
 ; outboundproxy
 ; rfc2833compensate
 ; callbackextension
-; registertrying
 ; timert1
 ; timerb
 ; qualifyfreq