xattrs: fix capabilities root test

Related discussion in the Fedora pull-request:
https://src.fedoraproject.org/rpms/tar/pull-request/8

* tests/capabs_raw01.at: Newer systems (currently e.g. Fedora 34)
print getcap output in format CAP=VAL, not CAP+VAL.

tests/capabs_raw01.at

@@ -44,10 +44,11 @@ rm -rf dir
 # restore _all_ xattrs (not just the user.* domain)
 tar --xattrs --xattrs-include='*' -xf archive.tar
 
-getcap dir/file
+# Newer systems print = instead of + here
+getcap dir/file | sed 's/+/=/'
 ],
 [0],
-[dir/file = cap_chown+ei
+[dir/file = cap_chown=ei
 ])
 
 AT_CLEANUP