chan_sip: Allow static realtime members to be qualified during module load.

When a static realtime peer with qualify=yes is loaded, Asterisk will fail to
send an OPTIONS request due to the lastms being equal to 0. This results in
the peer being unable to receive calls from Asterisk because the status is
permanently UNKNOWN.

This patch allows an OPTIONS request to be sent during module load by
ignoring the lastms value on startup only.

Review: https://reviewboard.asterisk.org/r/3294/

(closes issue ASTERISK-17523)
Reported by: Maciej Krajewski
Tested by: wushumasters
patches:
  realtime_fix_11.7.0.txt uploaded by Trevor Peirce (license 6112)
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Merged revisions 410105 from http://svn.asterisk.org/svn/asterisk/branches/1.8
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Merged revisions 410106 from http://svn.asterisk.org/svn/asterisk/branches/11


git-svn-id: http://svn.asterisk.org/svn/asterisk/branches/12@410107 f38db490-d61c-443f-a65b-d21fe96a405b