role:python: Set pip's Retry Interval to 0

[markuslf]

Make this setting configurable. Vendor default is 4, in a datacenter 0 would be a better default value.

With the vendor default an update with missing internet connection looks like this (and takes an hour):

Retrying (Retry(total=4, connect=None, read=None, redirect=None)) after connection broken by 'NewConnectionError('<pip._vendor.requests.packages.urllib3.connection.VerifiedHTTPSConnection object at 0x7f4b16cb3190>: Failed to establish a new connection: [Errno 101] Network is unreachable',)': /simple/python-dateutil/
Retrying (Retry(total=3, connect=None, read=None, redirect=None)) after connection broken by 'NewConnectionError('<pip._vendor.requests.packages.urllib3.connection.VerifiedHTTPSConnection object at 0x7f4b16cb7210>: Failed to establish a new connection: [Errno 101] Network is unreachable',)': /simple/python-dateutil/
Retrying (Retry(total=2, connect=None, read=None, redirect=None)) after connection broken by 'NewConnectionError('<pip._vendor.requests.packages.urllib3.connection.VerifiedHTTPSConnection object at 0x7f4b16cb7390>: Failed to establish a new connection: [Errno 101] Network is unreachable',)': /simple/python-dateutil/
Retrying (Retry(total=1, connect=None, read=None, redirect=None)) after connection broken by 'NewConnectionError('<pip._vendor.requests.packages.urllib3.connection.VerifiedHTTPSConnection object at 0x7f4b16cb7510>: Failed to establish a new connection: [Errno 101] Network is unreachable',)': /simple/python-dateutil/
Retrying (Retry(total=0, connect=None, read=None, redirect=None)) after connection broken by 'NewConnectionError('<pip._vendor.requests.packages.urllib3.connection.VerifiedHTTPSConnection object at 0x7f4b16cb7690>: Failed to establish a new connection: [Errno 101] Network is unreachable',)': /simple/python-dateutil/
Requirement already up-to-date: python-dateutil>=2.6.0 in /opt/python2-influxdb/lib/python2.7/site-packages (from influxdb)