[v9_11] Do not use escape codes for matching with grep
FreeBSD 13.0 replaced GNU grep with BSD grep and removed support for "redundant escapes for most ordinary characters" from regex(3) library, therefore the matching sequence in digdelv/tests.sh needs to be rewritten otherwise it fails with:
grep: trailing backslash (\)
(cherry picked from commit 253ae96b)
Closes #2692 (closed)