added missing force flag on mkfs commandline

even if the option ```force=yes``` is used in the playbook, it is not reflected in the mkfs command line.
As force option is dependent of the fs type, a "if-then-else" case have been added. Also, some FS types does not have a force option.

library/system/filesystem

@@ -95,10 +95,17 @@ def main():
     else:
         mkfs = module.get_bin_path('mkfs', required=True)
         cmd = None
+        if fstype in ['ext2', 'ext3', 'ext4', 'ext4dev']:
+          force_flag="-F"
+        elif fstype in ['btrfs']:
+          force_flag="-f"
+        else:
+          force_flag=""
+
         if opts is None:
-            cmd = "%s -t %s '%s'" % (mkfs, fstype, dev)
+            cmd = "%s -t %s %s '%s'" % (mkfs, fstype, force_flag, dev)
         else:
-            cmd = "%s -t %s %s '%s'" % (mkfs, fstype, opts, dev)
+            cmd = "%s -t %s %s %s '%s'" % (mkfs, fstype, force_flag, opts, dev)
         rc,_,err = module.run_command(cmd)
         if rc == 0:
             changed = True