generic/611: Use _getfattr instead of GETFATTR_PROG

When using old version(such as getfattr 2.4.46) getfattr command, it
has the following output,

touch file
setfattr -n user.a file
getfattr --absolute-names -n user.a file
user.a

on new getfattr, it reports the following output,
getfattr --absolute-names -n user.a file
user.a=""

The {=""} will break the golden image, so use _getfattr to filter
the redundant ="" at the end if it has.

Signed-off-by: Yang Xu <xuyang2018.jy@cn.fujitsu.com>
Reviewed-by: Eryu Guan <guaneryu@gmail.com>
Signed-off-by: Eryu Guan <guaneryu@gmail.com>

tests/generic/611

@@ -51,7 +51,7 @@ touch "${localfile}"
 _scratch_cycle_mount
 
 # If the target bug isn't fixed, getfattr fails
-${GETFATTR_PROG} --absolute-names -n user.a $localfile | grep 'user.a'
+_getfattr --absolute-names -n user.a $localfile | grep 'user.a'
 
 status=0
 exit

tests/generic/611.out

@@ -1,2 +1,2 @@
 QA output created by 611
-user.a=""
+user.a