Update Issue 21

Backport to TelScale branch

Committing patch from mitchell.ackerman@pgi.com, Thanks !
 and adding non regression test

git-svn-id: https://svn.java.net/svn/jsip~svn/trunk@2269 8e71dc83-d81e-6649-80f2-80b843a9b2be
(cherry picked from commit 63064352a698c3c21b9eb596e1c407f9c6657a9b)

Conflicts:
	src/gov/nist/javax/sip/stack/SIPServerTransactionImpl.java
	src/test/unit/gov/nist/javax/sip/stack/ServerTransactionRetransmissionTimerTest.java
Update Issue 28
(git-repo)

http://java.net/jira/browse/JSIP-444

Fix + non regression test
Update Issue 28
(git-repo)

http://java.net/jira/browse/JSIP-444

Fix regressions on testsuite and NPE discovered in logs of testsuite