fixed: restore w/ overwrite by linux client and split vss

setup:
win-client is a windows client configured w/ split_vss=1
linux-client os a linux client configured as restore_client for
win-client

problem:
when running the following on linux-client (note the -f option)

burp -C win-client -a r -f -d <restore path> -b <#backup> -r <regexp>

burp first overwrites any existing file at the destination w/ file
data and then overwrites that with the vss footer of each file

fix:
on linux: prevent overwrite of file when considering vss footer in
overwrite_ok
Merge pull request #131 from ZungBang/vss_remote_restore

fixed: restore w/ overwrite by linux client and split vss