Auto merge of #3220 - alexcrichton:bad, r=brson

Load [replace] sections from lock files

This commit fixes a bug in Cargo where path-based [replace] dependencies were
accidentally not loaded from lock files. This meant that even with a lock
file some compilations could accidentally become nondeterministic. The fix here
is to just look at all path dependencies, even those specified through [replace]

Closes #3216