evolve: set the second parent if we get conflicts while evolving This patch makes sure we set the second parent correctly if we run into conflicts while evolving. Also, we need to make sure to reset to one parent before committing.

evolvecmd: import mercurial.node module as nodemod We use node as a variable name at few places and the conflicts with variable name are not good. Moreover this practice is followed in core mercurial also.

tests: demonstrate the interrupted evolve does not set p2 This patch adds a test to demonstrate issue5927 which is about evolving not setting p2 correctly in interruption.