Treat FTL return data as strings

[yubiuser]

What does this PR aim to accomplish?:

Fixes a bug reported on Discourse: when FTL return a RegEx which fits a domain searched by with pihole -q it can error due to invalid escape. This only occurs because we use sh as shebang for the query script.

How does this PR accomplish the above?:

Replace echo calls with printf %s.

Fix confirmed working by OP on discourse.

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[yubiuser]

Mhh....

Setected x86_64 architecture\n  [i] Checking for existing FTL binary...\n  [i] Branch "development" is not available.