import: fix comma in capacity

This patch fixes error while importing image:
`nm_db_edit: database error: 8 values for 7 columns`

In some locales, there may be a comma instead of a period
in fractional numbers, which breaks the SQL query.

Closes #181

src/nm_database.h

@@ -310,13 +310,13 @@ static const char NM_SQL_DRIVES_INSERT_NEW[] =
     "INSERT INTO drives(vm_id, drive_name, drive_drv, "
     "capacity, boot, discard, format) "
     "VALUES((SELECT id FROM vms WHERE name='%s'), "
-    "'%s_a.img', '%s', %s, %s, %s, '%s')";
+    "'%s_a.img', '%s', '%s', %s, %s, '%s')";
 
 static const char NM_SQL_DRIVES_INSERT_ADD[] =
     "INSERT INTO drives(vm_id, drive_name, drive_drv, "
     "capacity, boot, discard, format) "
     "VALUES((SELECT id FROM vms WHERE name='%s'), "
-    "'%s_%c.img', '%s', %s, 0, %s, '%s')";
+    "'%s_%c.img', '%s', '%s', 0, %s, '%s')";
 
 static const char NM_SQL_DRIVES_INSERT_IMPORTED[] =
     "INSERT INTO drives(vm_id, drive_name, drive_drv, "