Verify that binaries exist before startVolumes calls them

defaults/initrd.scripts

@@ -598,8 +598,13 @@ startVolumes() {
 	fi
 	
 	if [ "${USE_MDADM}" = '1' ]
+	then
+		if [ -e '/sbin/mdadm' ]
 		then
 			/sbin/mdadm --assemble --scan
+		else
+			bad_msg "mdadm not found: skipping mdadm raid assembly!"
+		fi
 	fi
 
 	if [ "${USE_DMRAID_NORMAL}" = '1' ]
@@ -648,8 +653,13 @@ startVolumes() {
 	fi
 	
 	if [ "${USE_ZFS}" = '1' ]
+	then
+		if [ -e '/sbin/zpool' ]
 		then
 			/sbin/zpool import -N -a ${ZPOOL_FORCE}
+		else
+			bad_msg "zpool not found: skipping ZFS pool import!"
+		fi
 	fi
 }