CashSync when connected

Only perform cash sync if we are actually connected to IB
Related Issue

N/A

Motivation and Context

CashSync happening while gateway is restarting

Requires Documentation Change

N/A

How Has This Been Tested?

N/A

Types of changes
[x] Bug fix (non-breaking change which fixes an issue)
[ ] Refactor (non-breaking change which improves implementation)
[ ] Performance (non-breaking change which improves performance. Please add associated performance test and results)
[ ] New feature (non-breaking change which adds functionality)
[ ] Breaking change (fix or feature that would cause existing functionality to change)
[ ] Non-functional change (xml comments/documentation/etc)

[x] My code follows the code style of this project.
[x] I have read the CONTRIBUTING document.
[ ] I have added tests to cover my changes.
[x] All new and existing tests passed.
[x] My branch follows the naming convention bug-<issue#>-<description> or feature-<issue#>-<description>

QuantConnect / Lean.Brokerages.InteractiveBrokers