gopackagesdriver: ignore bazel analysis errors

Bazel exits with code 7 (ANALYSIS_FAILURE) when querying a file
that's not mentioned in BUILD. gopackagesdriver can returns partial
results for code 1 (BUILD_FAILURE), but not 7.

gopackagesdriver often hits this for a new file not added to BUILD.
A file= query may still fail in this case because the query will
match no labels, but at least that's no longer a bazel error.

For #4565