Fix reversed sense of vectorize enable flag

[dmk42]

In #9567 , explicit vectorization metadata was enabled when not using the Region Vectorizer, causing messages about failed vectorization to print out. This causes some tests to fail.

This happened because the metadata was enabled when not using the RV, and disabled when using the RV. I believe it was meant to be the other way around.

Here is an example of the extraneous messages.

remark: <unknown>:0:0: loop not vectorized: call instruction cannot be vectorized
remark: <unknown>:0:0: loop not vectorized: call instruction cannot be vectorized
warning: <unknown>:0:0: loop not vectorized: failed explicitly specified loop vectorization
warning: <unknown>:0:0: loop not vectorized: failed explicitly specified loop vectorization

[dmk42]

@mppf - Would you please do a post-commit review?

[mppf]

@dmk42 - thanks for the fix - I believe you are right about this