This "NoAutoMount" member was not consistently used. Sometimes it was
used correctly, some other times it was used as "not NoAutoMount" i.e.
"AutoMount" enabled.
Fix this consistently throughout the source, and fix also some comments.
- Do not access uninitialized SymlinkInformation on failure case
and just return
- Do not make an assumption that MOUNTMGR_TARGET_NAME has a zero-string
- ReparseFile was concatenated with itself, instead of ReparseIndex
- Meanwhile, use RtlAppendUnicodeStringToString for concatenating
strings instead of raw memory operations
