3.5 install/restore from UNC share has performance Regression from 3.4.4

[zhili1208]

issue:
Compared the time of Gathering dependency information for all packages from UNC share.

3.4.4

First access for one package time: 2.85 seconds (slow UNC share, do not check feed type at that time)
Then 10 times access for same package time: 2 ms. (v2 local repo memory Cache)

3.5
First access for one package time: around 8.1 seconds (2.13 seconds for gathering package information, around 6 seconds for determining source feed type)

Then 10 times access for same package time: around 60 seconds (6 second for determining source feed type for each access, used gather cache for gathering package information)

3.5 with Cache feed type.

First access for one package time: 4.17 second (2.13 second for gathering package information, around 2 second for determining source feed type)

Then 10 times access for same package time: 25 ms ( around 2ms for each, used gather cache for gathering package information)

the bug is source feed type is not cached