HPCC-12298 hpcc_common start time and thor sentinel changes

Signed-off-by: Michael Gardner <Michael.Gardner@lexisnexis.com>
It's prob okay for now (because most are not checking sentinel), because Thor should take >60s, but I'm concerned this will cause spurious failure messages if some component did take >60s to start , e.g. Dali (see earlier comment). 

Perhaps the '.. but may still be starting' should be the default message under these circumstances.