agreement: fix fuzzer test NetworkFacade Clock implementation

[cce]

Summary

There was one Clock implementation not updated in #3703 in the agreement fuzzer testing package's NetworkFacade type. This updates it to fully implement the Clock interface.

[codecov-commenter]

Codecov Report

Merging #3716 (e56fa43) into master (f919bb8) will increase coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #3716      +/-   ##
==========================================
+ Coverage   49.57%   49.58%   +0.01%     
==========================================
  Files         391      391              
  Lines       68577    68577              
==========================================
+ Hits        33998    34005       +7     
+ Misses      30844    30840       -4     
+ Partials     3735     3732       -3     

Impacted Files	Coverage Δ
ledger/roundlru.go	90.56% <0.00%> (-5.67%)	⬇️
cmd/algoh/blockWatcher.go	77.77% <0.00%> (-3.18%)	⬇️
network/wsNetwork.go	62.79% <0.00%> (-0.20%)	⬇️
network/wsPeer.go	68.61% <0.00%> (+0.55%)	⬆️
ledger/acctupdates.go	69.08% <0.00%> (+0.66%)	⬆️
cmd/tealdbg/debugger.go	72.41% <0.00%> (+0.98%)	⬆️
ledger/blockqueue.go	85.05% <0.00%> (+2.87%)	⬆️

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