yt set --recursive does not work for attributes when parent attribute or node is missing

All combinations are broken. One report false-positive success.

```
yt set -r "//home/$USER/a/b/@c/d" 1

Expected "literal" in YPath but found "at" token "@"
```

```
yt set -r "//home/$USER/@c/d" 1

Custom attribute "c" is not found
```

```
yt set-attribute //home/$USER/a/b c/d 1

Attribute commands forbid to use '/' in attribute names
```

```
yt set-attribute -r //home/$USER/a/b c/d 1

Node //home/khlebnikov has no child with key "a"
```

```
yt set-attribute -r //home/$USER c/d 1
(success!)

yt get //home/$USER/@c/d

Attribute "c" is not found
```