improve search tests to wait for no 425 in PROPFIND response

[individual-it]

in search tests we wait for some time till the indexing is finished, see https://github.com/opencloud-eu/opencloud/pull/1802/commits/76713480e3c16d2ae90ac928b928b5ee31ee7d99

this sleep could be reduced if we wait for no 425 in the PROPFIND response. As long as there is a 425 retry the search.

see also https://github.com/opencloud-eu/qa/issues/50#issuecomment-3498369410 and the next comments

[individual-it]

alternative could be solved by #1804