[krbdev.mit.edu #8605] OS X SIP breaks some tests in "make check"

[Greg Hudson via RT]

t_iprop.py also hangs in this version of macOS with SIP enabled, right 
after starting the first kpropd process and waiting for sync:

*** [20] Started with pid 32658
*** Waiting for sync from kpropd
kpropd: Incremental propagation enabled
kpropd: waiting for a kprop connection
kpropd: Initializing kadm5 as client kiprop/localhost at KRBTEST.COM
kpropd: kadm5 initialization succeeded
kpropd: Calling iprop_get_updates_1 (sno=1 sec=1502837269 usec=765479)
kpropd: Full resync needed
kpropd: Full resync request granted
kpropd: Waiting for 600 seconds before checking for updates again

A possible theory is that the listener child is unable to signal its 
parent that the dump completed.  Most likely we will need to find a 
way to detect this restriction and skip t_iprop.py if it is in force, 
since rearchitecting kpropd and its tests not to use signals would be 
a tall order.