robust create user: allow new userid to be to generate a new random one; handle possible case of a weareble being a inventory link

Author	UbitUmarov <ajlduarte at sapo dot pt>
Author date	2018-04-14 22:05:46
Author local date	2018-04-14 23:05:46 +0100
Committer	UbitUmarov <ajlduarte at sapo dot pt>
Committer date	2018-04-14 22:05:46
Committer local date	2018-04-14 23:05:46 +0100
Commit	7c9c5cfedf90d7589386f4dddc6879c0734a0429
Tree	2febae4da3c4cb73c29fc8dd6134aacac55c3f50
Parent	90482182e569218af86b20dca24a0792ec7ffaae

 robust create user: allow new userid to be  to generate a new random one; handle possible case of a weareble being a inventory link

Affected files:
OpenSim/Services/UserAccountService/UserAccountService.cs