rd_acquire() error handling is adjusted to match libdbus error
handling convention:
 * Initialize error before calling rd_acquire()
 * Free dbus error on rd_acquire() failures
 * Always set dbus error on rd_acquire failures, except for
   detected programming errors that now cause taboo assert.

git-svn-id: http://subversion.jackaudio.org/jack/jack2/trunk/jackmp@4395 0c269be4-1314-0410-8aa9-9f06e86f4224

git-svn-id: http://subversion.jackaudio.org/jack/jack2/branches/libjacknet@3614 0c269be4-1314-0410-8aa9-9f06e86f4224

git-svn-id: http://subversion.jackaudio.org/jack/jack2/trunk/jackmp@3603 0c269be4-1314-0410-8aa9-9f06e86f4224

git-svn-id: http://subversion.jackaudio.org/jack/jack2/branches/libjacknet@3354 0c269be4-1314-0410-8aa9-9f06e86f4224

git-svn-id: http://subversion.jackaudio.org/jack/jack2/trunk/jackmp@3342 0c269be4-1314-0410-8aa9-9f06e86f4224