scripts/build-and-provide-package: replace egrep usage with grep -E
scripts/build-and-provide-package: replace egrep usage with grep -E

grep 3.8 deprecated support for egrep + fgrep, and now prints a warning on stderr:

| egrep: warning: egrep is obsolescent; using grep -E
| fgrep: warning: fgrep is obsolescent; using grep -F

mika/jenkins-debian-glue,mika/jenkins-debian-glue