FIX: validate MAINIP without so-common during setup

setup runs so-minion -o=setup before /usr/sbin/so-common is installed, so
valid_ip4 was undefined, every MAINIP was rejected, and no minion pillar
was written. Pillar compile then failed for the new manager and setup gave
up waiting for the salt master. Use an inline IPv4 regex instead.

salt/manager/tools/sbin/so-minion

@@ -1078,6 +1078,9 @@ function updateMineAndApplyStates() {
 # Values end up in a Jinja-rendered pillar and in bash, and may come from the minion
 function validate_minion_vars() {
 	local error_msg=""
+	# Inline rather than valid_ip4: so-common is not installed yet when setup runs -o=setup
+	local octet='(25[0-5]|2[0-4][0-9]|1?[0-9]?[0-9])'
+	local ip4_re="^($octet\.){3}$octet$"
 
 	case "$NODETYPE" in
 		EVAL|STANDALONE|MANAGER|MANAGERSEARCH|MANAGERHYPE|IMPORT)
@@ -1092,7 +1095,7 @@ function validate_minion_vars() {
 	esac
 
 	if [[ -z "$error_msg" ]]; then
-		if ! valid_ip4 "$MAINIP"; then
+		if [[ ! "$MAINIP" =~ $ip4_re ]]; then
 			error_msg="Invalid MAINIP: ${MAINIP:0:64}"
 		elif [[ ! "$MNIC" =~ ^[A-Za-z0-9._-]*$ ]]; then
 			error_msg="Invalid MNIC: ${MNIC:0:64}"