HPCC-12128 - MP connections take too long

When A-> B and B->A within a very short time frame a 3 minute delay would often occur after which a failed connection might still occur.  This was noticed very often when using the mptests, which are used for new mp lib development.

Signed-off-by: Mark Kelly <mark.kelly@lexisnexis.com>
I wanted a fence for the attachep and attachrand.  Perhaps I could remove the CS and add a fence but its a one-time or rare event.