lib: fix regcomp error processing

lib: fix regcomp error processing

 * use actual error code instead of "false"
 * add missing new line

Before:
```
nfware# show interface | include (a]
% Regex compilation error: Success% Bad regexp '(a]'
% Unknown command: show interface | include (a]
```

After:
```
nfware# show interface | include (a]
% Regex compilation error: Unmatched ( or \(
% Bad regexp '(a]'
% Unknown command: show interface | include (a]
```

Signed-off-by: Igor Ryzhov <iryzhov@nfware.com>