FreeNAS/freenas 9d1d9d4src/freenas-installer/etc install.sh

[install.sh] Simplify pipelines involving awk

Awk has its own pattern matching functionality, so grep before awk can
be eliminated.
Selecting a fixed field can be more efficiently performed with cut.
Misc whitespace/punctuation fixes.

This has no functional change, just needed a commit so we can do this:

DEPENDS: https://github.com/freenas/build/tree/feat-47015
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+8-8src/freenas-installer/etc/install.sh
+8-81 files

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