backglue and back-monitor clash in tools (ITS#3254)

[hyc@OpenLDAP.org]

Full_Name: Howard Chu
Version: HEAD,RE22
OS: 
URL: ftp://ftp.openldap.org/incoming/
Submission from: (NULL) (24.126.120.178)
Submitted by: hyc


In tool mode, backglue invokes backend_startup(NULL) which starts up all
configured backends. If back-monitor is configured, startup fails because
back-monitor cannot find any listener info. (There are no listeners since it is
running in tool mode.)

Not sure whether to fix backglue to be more selective or change back-monitor to
do recognize it's running in tool mode. ?