Add 'net rpc join' to match the ADS equiv.
This kills off the offending code in smbpasswd -j -Uab%c
In the process we have changed from unsing compelatly random passwords
to random, 15 char ascii strings. While this does produce a decrese in
entropy, it is still vastly greater than we need, considering the application.
In the meantime this allows us to actually *type* the machine account
password duruign debugging.
This code also adds a 'check' step to the join, confirming that the
stored password does indeed do somthing of value :-)
Andrew Bartlett