fix for checking CLEAN-ness of ramdisk image

. pre-cleanflag ("old") mkfs generates without CLEAN flag,
	  causing boot not working because imgrd disappears after 1st
	  close
	. fixed sanity check for this situation
	. disable imgrd disappearing in memory driver so
	  readonly mount succeeds in case it happens anyway

drivers/memory/memory.c

@@ -526,6 +526,7 @@ PRIVATE int m_block_close(dev_t minor)
   }
   openct[minor]--;
 
+#if 0
   /* Special case: free initial ramdisk after it's been unmounted once. */
   if(minor == IMGRD_DEV && openct[minor] == 0 && m_vaddrs[IMGRD_DEV]) {
 	vir_bytes vaddr, vlen;
@@ -547,6 +548,7 @@ PRIVATE int m_block_close(dev_t minor)
 	m_geom[IMGRD_DEV].dv_size= cvul64(0);
 	m_vaddrs[IMGRD_DEV] = 0;
   }
+#endif
 
   return(OK);
 }

drivers/ramdisk/Makefile

@@ -47,6 +47,7 @@ image:	proto.gen mtab rc $(EXTRA)
 	then	: ;	\
 	else	echo "CLEAN sanity check of image failed."	;	\
 		echo "(Perhaps install current mkfs and fsck.)" ;	\
+		rm -f image; false;             \
 	fi
 
 ahci: ../ahci/ahci