fix: skip dep->targetEdge conflict check when placing if there is a current node

[lukekarrys]

Fix: npm/cli#3881

When placing a peer set containing a dependency that could not be placed
higher in the tree due to a conflict, the entire peer set would get
nested even though the current node would satisfy the condition at the
target.

For example:

root -> (k, y@1)
k -> (x)
x -> PEER(y@1||2)

When placing x it would previously result in a tree with x nested
under k even though it can be properly hoisted to the root:

root
+-- k@1
|   +-- x@1
+-- y@1

After this patch the tree will now result in x being properly hoisted:

root
+-- k@1
+-- x@1
+-- y@1

Co-authored-by: @isaacs

[isaacs]

The only thing i would add to the commit message is saying that the reason it was being nested was because the peerSet includes a newer version that cannot be placed in the root, but which would not be placed at all anyway.

if the root could accept y@2, but just happened to have y@1, then it would have ended up being REPLACE instead of KEEP

But either one is not CONFLICT, so in either case, the right thing to do is not short-circuit, but instead continue on and see what we ought to do with the current node.