cifs: fix smb3_zero_range for Azure

For zero-range that also extend the file we were sending this as a
compound of two different operations; a fsctl to set-zero-data for the range
and then an additional set-info to extend the file size.
This does not work for Azure since it does not support this fsctl which leads
to fallocate(FALLOC_FL_ZERO_RANGE) failing but still changing the file size.

To fix this we un-compound this and send these two operations as separate
commands, firsat one command to set-zero-data for the range and it this
was successful we proceed to send a set-info to update the file size.

This fixes xfstest generic/469 for Azure servers.

Signed-off-by: Ronnie Sahlberg <lsahlber@redhat.com>
Signed-off-by: Steve French <stfrench@microsoft.com>