[stable12] do not catch and ignore ServerNotAvailable in the wrong spot

[blizzz]

backport of #8069

[codecov]

Codecov Report

Merging #8074 into stable12 will increase coverage by <.01%.
The diff coverage is 25%.

@@              Coverage Diff               @@
##             stable12    #8074      +/-   ##
==============================================
+ Coverage       53.84%   53.84%   +<.01%     
- Complexity      22760    22761       +1     
==============================================
  Files            1385     1385              
  Lines           87148    87150       +2     
  Branches         1331     1331              
==============================================
+ Hits            46926    46928       +2     
  Misses          40222    40222

Impacted Files	Coverage Δ	Complexity Δ
apps/user_ldap/lib/Access.php	18.15% <ø> (ø)	305 <0> (ø)	⬇️
apps/user_ldap/lib/User_LDAP.php	73.57% <25%> (-0.61%)	74 <0> (+1)
apps/files_trashbin/lib/Trashbin.php	72.28% <0%> (-0.25%)	136% <0%> (ø)
core/js/js.js	61.94% <0%> (+0.11%)	0% <0%> (ø)	⬇️
lib/private/Server.php	84.8% <0%> (+0.12%)	121% <0%> (ø)	⬇️
lib/private/Files/Cache/Propagator.php	96.2% <0%> (+1.26%)	16% <0%> (ø)	⬇️