Fix issue with invoke tag that has control flow

[DylanPiercey]

Description

Currently there is a bug with the invoke tag migration where it will incorrectly read the attributes before they are normalized by the common transformers.

This causes an issue where an invoke tag contains control flow:

<invoke if(x) y()/>

Which will error at compile time before this fix.

Checklist:

• I have read the CONTRIBUTING document and have signed (or will sign) the CLA.
• I have updated/added documentation affected by my changes.
• I have added tests to cover my changes.

[coveralls]

Coverage remained the same at 90.591% when pulling b7fafdd on invoke-tag-with-control-flow into b264a27 on master.

[codecov]

Codecov Report

Merging #1366 into master will not change coverage.
The diff coverage is 100%.

@@           Coverage Diff           @@
##           master    #1366   +/-   ##
=======================================
  Coverage   90.59%   90.59%           
=======================================
  Files         341      341           
  Lines       12467    12467           
=======================================
  Hits        11294    11294           
  Misses       1173     1173

Impacted Files	Coverage Δ
src/core-tags/migrate/invoke-tag.js	83.33% <100%> (ø)	⬆️

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