Fix a bug that DealerSocket has been broken after IBD.

[longfin]

This PR fixes a bug that Swarm had not dial to other peer after IBD. This is due to the fact that Swarm's internal DealerSocket doesn't connect properly after a certain period of time.

To solve this problem, every DialAsync() has been modified to close the previous DealerSocket and create a new DealerSocket.

[longfin]

/rebase

[autorebase]

The rebase failed:

Not Found

To rebase manually, run these commands in your terminal:

# Fetch latest updates from GitHub.
git fetch
# Create new working tree.
git worktree add .worktrees/rebase bugfix/fix-dial-after-ibd
# Navigate to the new directory.
cd .worktrees/rebase
# Rebase and resolve the likely conflicts.
git rebase --interactive --autosquash master
# Push the new branch state to GitHub.
git push --force
# Go back to the original working tree.
cd ../..
# Delete the working tree.
git worktree remove .worktrees/rebase

[codecov]

Codecov Report

Merging #311 into master will increase coverage by 0.05%.
The diff coverage is 80%.

@@            Coverage Diff             @@
##           master     #311      +/-   ##
==========================================
+ Coverage   87.34%   87.39%   +0.05%     
==========================================
  Files         189      189              
  Lines       12741    12744       +3     
==========================================
+ Hits        11129    11138       +9     
+ Misses       1361     1355       -6     
  Partials      251      251

Impacted Files	Coverage Δ
Libplanet/Net/Swarm.cs	74.88% <80%> (-0.17%)	⬇️
Libplanet.Tests/Net/SwarmTest.cs	93.75% <0%> (+1.24%)	⬆️