HPCC-12128 - MP connections take too long

Resolve mp connection deadlock when A->B and B->A with lower random number

Signed-off-by: Mark Kelly <mark.kelly@lexisnexis.com>
probably slightly clearer if inc was in same object as dec.
i.e.:
```
    struct attachCounter
    {
        atomic_t &attchk;
        attachdTor(atomic_t &_attchk) : attchk(_attchk) { atomic_inc(&attchk); }
        ~attachdTor() { atomic_dec(&attchk); }
    } attachChk (attachchk);
```