Ignore cargo output in all directories, not just virtualizationservice.

Test: built idsig crate with cargo, checked git status
Change-Id: I624e6c63b8481c5b4d86f4382f3bd9ba2a48e9b9
diff --git a/virtualizationservice/.gitignore b/.gitignore
similarity index 100%
rename from virtualizationservice/.gitignore
rename to .gitignore