adds default web response timeout of 120 seconds

[techyragu]

• Adds default time out of 120 Sec at ImcHandle level and across individual ImcHandle APIs.
• Adds method to modify and reset web response timeout.

>>> handle.login()
True
>>> handle._ImcHandle__response_timeout
120
>>>
>>> handle.set_response_timeout(60)
>>> handle._ImcHandle__response_timeout
60
>>>
>>> handle.reset_response_timeout()
>>> handle._ImcHandle__response_timeout
120```

Signed-off-by: Rahul Gupta <ragupta4@cisco.com>

[vvb]

@ragupta-git Any specific reasoning behind choosing 120?