Fix long-standing memory leak as found by Jerry Nichols
bob Cleartext-Password := "hello"
Tunnel-Server-Endpoint := 1.2.3.4,
Tunnel-Server-Endpoint := 1.2.3.5,
Tunnel-Type := 3,
Tunnel-Server-Endpoint := 1.2.3.2,
Tunnel-Medium-Type := 1,
Tunnel-Server-Endpoint := 1.2.3.1
Where there are multiple copies of
the same attribute with a := operator in the 'from' list, and the only
operators in the 'from' list are :=, then all the repeated attributes
after the first and before the last non-repeated attribute are lost. In
the example above that would result in the VALUE_PAIRS :
Tunnel-Server-Endpoint := 1.2.3.5
Tunnel-Server-Endpoint := 1.2.3.2
being orphaned.