LVM error causing fall back to initramfs on boot after ubuntu upgrade

Question

I've recently updated Ubuntu from an older LTS release (12.04) to 14.04 LTS and upon reboot, ubuntu fails to load and an error in /sbin/lvm is shown:

There appears to be one or more degraded LVM volumes, and your root device may 
depend on the LVM volumes being online. 
One or more of the following LVM volumes are degraded:
/sbin/lvm: symbol lookup error: /usr/local/lib/libreadline.so.5: undefined symbol: PC
Gave up waiting for root device...
ALERT! /dev/mapper/my-server-root does not exist. Dropping to a shell!

It seems like the /sbin/lvm: symbol lookup error: /usr/local/lib/libreadline.so.5: undefined symbol: PC is the culprit, and I suppose that /sbin/lvm wasn't correctly linked with the appropriate libraries, causing the boot image to be unable to run LVM at all, so the LVM volumes does not load.

What I have tried

1. Running lvm in the initramfs shell returns the same error about symbol lookup.

2. Removing /usr/local/lib/libreadline.so.5 and running lvm will make it throw an error about libreadline.so.5 not being available instead.

3. vgchange is not a valid command (I assume it requires lvm and it should be ran using lvm vgchange -ay instead?)

I guess that I should try to re-build the boot image to include a correct copy of lvm. However I am not sure how to do that (should I boot a 14.04 live disk, and install lvm2, or should I do some more steps? How can I modify initramfs and fix it?) and I am afraid I mess up the existing LVM configuration. How should I do that? Thanks!