chan_agent: Misc code cleanup.

* Fix off-nominal path resource cleanup in agent_request().

* Create agent_pvt_destroy() to eliminate inlined versions in many places.

* Pull invariant code out of loop in add_agent().

* Remove redundant module user references in login_exec().

* Remove unused struct agent_pvt logincallerid[] member.
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Merged revisions 378456 from http://svn.asterisk.org/svn/asterisk/branches/1.8
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Merged revisions 378457 from http://svn.asterisk.org/svn/asterisk/branches/11


git-svn-id: http://svn.asterisk.org/svn/asterisk/trunk@378458 f38db490-d61c-443f-a65b-d21fe96a405b
Add missing test event

This test event was missing from channel.c causing the dial_LS_options
test to fail intermittently because of a race condition where most code
paths emitted the test event but this one did not. The dial_LS_options
test should stop bouncing now.
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Merged revisions 378455 from http://svn.asterisk.org/svn/asterisk/branches/1.8
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Merged revisions 378459 from http://svn.asterisk.org/svn/asterisk/branches/11


git-svn-id: http://svn.asterisk.org/svn/asterisk/trunk@378460 f38db490-d61c-443f-a65b-d21fe96a405b