Use grep -qE instead of egrep which is deprecated.

Signed-off-by: Stefan Staudenmeyer <doerte@instana.com>

hack/install.sh

@@ -372,7 +372,7 @@ do_install() {
 
 			# aufs is preferred over devicemapper; try to ensure the driver is available.
 			if ! grep -q aufs /proc/filesystems && ! $sh_c 'modprobe aufs'; then
-				if uname -r | grep -q -- '-generic' && dpkg -l 'linux-image-*-generic' | egrep '^ii|^hi' 2>/dev/null; then
+				if uname -r | grep -q -- '-generic' && dpkg -l 'linux-image-*-generic' | grep -qE '^ii|^hi' 2>/dev/null; then
 					kern_extras="linux-image-extra-$(uname -r) linux-image-extra-virtual"
 
 					apt_get_update