Bug 35173: Correctly concat error strings

Bug 35173: Correctly concat error strings

This patch moves the call to $sftp->error outside of the double quote
string and into a . concat to properly expose the error message as
apposed to outputting 'Net::SFTP::Foreign=HASH(0x559c9118f0c8)->error'

Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
(cherry picked from commit 43bd124f873ac118a9f87a5b5160ee99dc8b8a47)
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>