Change OWA timeouts

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MSExchangeOWA
Name: PublicTimeout
Type: DWORD
Value: {value in minutes} (This value is 15 minutes by default)

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MSExchangeOWA
Name: PrivateTimeout
Type: DWORD
Value: {value in minutes} (This value is 8 hours by default)